Geiger Bot is a iOS app that connects to Geiger counters and displays CPM and uSv/h on your iPhone or iPad.  It's available free at the App Store.

The Geiger Kit has been shown to work well with Geiger Bot. (Thanks to Atomic Dave for the integration, testing and and the setup materials below.) 

The following shows how to make the connection cable and set it up.

The diagram below shows how you wire up the cable to connect the Geiger Kit to the microphone jack on your iPhone or iPad. (click for larger image)

At the Geiger Kit, the signal side of the cable connects to the interrupt ("pulse in") on the Geiger. This is Pin 2 on the header. You can cannibalize an Apple headset to get the propitiatory 4 conductor plug. You can use the headset cable or some other appropriate cable. Be careful with the type of cable you use, and how it's routed. It can pick up noise and give high phantom counts. The diagram above is just a rough example. Finally, you need .1uf capicitor and the 56k and 1k resistors. (Note that the .1uF cap shouldn't be necessary because it is already in-line with the INT signal, however I've heard it works better with one.)

The image below shows how Dave set up the App on his iPhone.  (click for larger image)

Note that it's best to have Auto Adjust ON for background and non-alpha tubes. However at very high count rates, Auto Adjust should be turned OFF. In any case you may have to play with that setting.