simple android gps sender

i need a small and simple app for android phones, that does the following: * send the current coordinates and maybe the (compass) direction to my server every e.g. 15 or 30 seconds with a json call as long as the app is running * no map or geocoding is needed - just show the simple main screen, which i will according to your requirements and which will basically only show my logo, a switch where the user can switch logging on and off and some status showing if the current position has been sent to the server. i do not want to show a map or geocoding info in order to keep data traffic and energy consumption low and not to consume too many resources on the phone. * there also needs to be some simple login screen (username/pin) with the data entered remembered by the app on future starts * if possible, the app should keep running and sending in the background, if the user starts to use some other app or makes a phone call * i am new to android, so i'd please need advise regarding design for the screens and on compatible phones. basically the app should be able to run on the cheapest possible android phones so that i can use cheap phones and the app as a cheap tracking solution. if you need more information, please let me know. thanks a lot. martin.