This is a clock and mini-game app for both Android and iOS. The original version (more or less an incomplete beta) was released in October 2011. Better functionality came in early 2012 with version 1.5 (the latest is 1.7 updated back in Feb 2013.) The full version is around $6 (unlocks the rest of the options on the main screen). And that is all it does; unlocks the other options where you get to spend more money.
I forgot to take a screenshot of the US version before I purchased the full version so the following are images I found online from the Japanese version. The free download has only Information and Costume as available options. Regardless of version, you have to go into the Costumes option and select the first button (I added the english text in the 2nd image) to be able to purchase the full version. The other costumes include a sailor outfit, swimwear, and shirt.
Once purchased, the other options unlock. The unlocked version is a VERY mini Dream C Club game where you can similarly try to get a better impression with her (filling the heart) since you can buy her in-game drinks and presents; WARNING! both cost real money on a per use basis (infinite drinks cost $6 and infinite presents cost $12 - both are ultimately cheaper than paying individually since all possible presents cost over $18 and each drink is something like 99 cents for a Dream Cocktail Light and $1.99 for a Dream Cocktail Magma.) Drinks and presents are consumable one time use only! Unlike the console games, there is no way in this app to earn in-app currency. The following are images I got online from an older Japanese version of the app before they added an "infinite" option for drinks and presents.
The following are my screenshots from the most recent US version (1.7) where each DLC category has an option to purchase everything (I forgot to capture the one for drinks and presents.) so the second and third images are what those DLC's look like after purchasing the infinite options (so I can just buy as many to keep Amane happy and content.)
The first image below is the Options screen (I added the English text) from the US version. You can reset the impression (back to no filled heart), her sobriety state, enter your birthdate (which probably has her giving you a happy birthday message that likely fills a Memory slot), a restore purchases option, and a FAQ button that takes you to their website. The second image is self-explanatory.
The app itself centers around hostess Amane (as with most of these sort of clock apps, touching her and moving your device around will invoke different looks, reactions, and comments). There is nothing hentai related though when touching her (well except if you try and touch her chest, she will speak her disproval). Amane will announce the time when tapping on it (this too only works with the full version.) Shaking your smart device rapidly for example will show her sort of spinning and saying how this is making her dizzy; one time, she started blurting out "ya-me-te ku-da-sa-i" (please stop it) in a wavering sound which matched the rapid shaking. If you rub her tummy area, she may say she either likes it or not. It uses the Live2D imaging engine which results in very smooth animation. I have to be honest; Amane's rendering with this graphics engine looks way better than her appearance on the consoles (fangirl moment: her movements and expressions at times are just too cute and adorable.)
I created this YouTube playlist with screen recordings of some of the above.
For anyone who has played any of the Dream C Club games, you'll know about the electronics communication part (text messages and e-mail). Well D3 Publisher actually made it where you can get similar notifications where the app will ring your device (using the default ringtone that exists in the Dream C Club games) as if a real call/message was incoming from Amane herself. It's a one-sided conversation of course but is part of the mini-game that can take you by surprise if you allow the game to perform notifications/sounds to your lock screen. Once encountered, this fills a slot in the Memory option (see below).
There is a slight problem I encountered at least on iOS though; when this notification came in when the device was locked, there was no way to get the fake keitai screen and her message to come up unless you explicitly set the app to put up a notice on the lock screen (you can then swipe across that notification, unlock the device, and it will bring up the app with the fake keitai screen with the message.) And if this notification came in while the device was unlocked, the same issue existed unless I set it to an alert style (this pops up the old dialog box which requires an action to proceed.) I noticed this when my phone began beeping and the banner style alert notified me it was Amane; but there was no way to access the message since launching the app would only bring you to the usual main clock screen.
The Memory option contains conversation pieces that fill based on presents, interacting on a daily basis, and messages on certain days of the year (like one or two slots are for Christmas for example.) Tapping on any one of these will allow playback of her conversations. One of the cutest ones is where she counts and begins falling asleep (see the following YouTube video of this.)
The camera option places an overlay of Amane over either your live camera scene OR you can choose an existing image from your device to do the same. Pinching in/out resizes Amane. When you click the shutter button, she announces a really cute "cheezu" (the DCC fangirl in me squeals "kawaii" at this point.) You can come up with silly, dorky and potentially f*cked up and embarrassing pictures. Yes, Amane is really sweet <_<!
Opinion: this app was probably D3 Publisher testing the waters for an actual interactive touch-based version of Dream C Club but I doubt they made a lot of money from this because the entire pricing was way off the mark. This clock is one expensive "game" when you total up the initial unlock and all DLC's (plus a hack later came out which made it fairly easy to unlock all the in-app purchases and all memory conversations since all of that data is stored in a plain text file.)
You'll probably also have noticed the app has a wild mix of English and Japanese text localization. The only differences between the Japanese and US versions are the way the prices are denoted (in local currency.) I talked to someone more versed in smartphone app development; despite the fact the app is available on non-Asian iTunes and Google Play stores and there is English text in the DLC part, doesn't mean there was an actual effort to capture a large amount of sales from a non-Asian market; this just seems to be an outcome of how the app and its assets were developed as well as deploying it onto each companies respective app store.
With regards to the hack, it is applicable to Android and iOS versions; the latter does not require a jail break since it does not modify the actual program. I'm not going to link that information here though for obvious reasons.