Need to develop a spped limit warning app for android blackberry and iphone (later windows phones as well).
The app will be remotely controlled by a sms (hidden on the receiving phone) which will set a speed limit and activate gps.
If the speed limit is exceeded the app will return a sms (hidden on the sending phone) with actual speed.
On set up you might be able to choose between miles or km.
The installed app needs to be on stealth mode (hidden to the pone's user) and uninstallable unless an sms is received.