My wife and I would like to be able to track our two teenaged sons whereabouts. I have been playing with several apps. My wife and I and one son has an android phone, while the other son has an iphone. Can someone recommend a good app to do this? I don't mind paying for the app, but don't want a monthly fee. Also, by the time we all download and find out if the app is good, the return time will expire. Any help is appreciated!