One of the cool things about the iphone4s, is the ability to send a message based on location. A great feature although a primary culprit for the battery issues when the iphone4s came out. There are a few other app that do something like this so I decided to give them a try.
First is Dropp. The man point of this app is not to serve as a location based reminder system but instead an interesting way to leave notes based on location. I tried it and it works as expected. However, you have to have the app running for precises location matching so this provides limited functionality if you want to protect the iphones battery life. The good news is if you do not need precise location detection, the app can use wifi reckoning which, although not as accurate, will not suck up your battery. A second issue is that it only displayed a note, it does not send a message.
The next app just came out. Called iSms@Spot is is more focused on performing the single act of sending a message based on location however different from Dropp, it will send a message, email, SMS and iMessage. This is most useful if you need to alert someone else once you arrive at a location. However, I do like to use it to send SMS reminder messages while I’m driving.
So both apps will do what you need as far as getting an alert once you enter a certain location, however they both have the same limitation if you need precise location detecting which requires the GPS and the app has to be running and can greatly reduce your battery life. so hopefully you keep your iphone plugged in at home as well as in the car. However, in most cases, using wifi reckoning should be good enough.