GeoMessaging is an easy way to trigger the automatic sending of an email message to one or more contacts when your iPhone crosses a selected location on the map.
It's simple: enter your message (what), select the trigger region (where), and choose your recipients (who). But first don't forget to configure the email account that will be used to send the message (how). You can use a GMail, Hotmail, Yahoo or MobileMe email account. Once a Tripwire is triggered you will get an alert and an email is sent out to your recipients.
Now why in the world would you want to do that?
Avoid texting-and-driving. Ever find yourself already driving and remembering you should have sent that message before you got in the car? Set up a Tripwire and let it send out your message telling your loved one you just left work.
Notify someone that you're on the way or that you're almost there. Put a Tripwire message around the cinema metro station to tell your friends to save you a seat.
Send yourself a reminder of when you performed an activity in a certain location. Wonder what time you crossed the bridge during your biking run? Tripwire it and you'll have a timestamped message in your inbox.
Text-and-bike. Whether on a bicycle or motorcycle you can pre-set a message to your roommates telling them to save you some pizza because you are only a few blocks away.