I second the suggestion that you should install Gentoo Mobile. Its open-source, Linux based and way more secure than Android.
Your friend is using Remote access to fuck with you. Install Stuxworm onto your Android device, if it already isn't shipped with it (Most Android handsets, ship with Stuxworm/stuxnet).
Also, you can reverse track your friend if you run a small network access trace on your Radio stack, this will display all the addresses your phone is accessing, you should be able to filter out your friends IP Address from this, and do a remote install on his phone/computing device.
Also, don't forget to use DuckDuckGo as it has the "Don't track us" and "Don't bubble us" option, you should go to
http://ddg.gg right away and check it out. Also change it to be your default search provider as Google can be made to send your browsing history to a third party (in this case your friend has set it up such that he receives logs about your browsing habits.
Try confronting him about this, and this is the only proper way for this to be resolved. If you're no longer in talking terms with said former friend, try and learn Sign language so that you can just communicate with him without actually talking to him. Also, he can see text messages that you send to him, so stop sending him text messages! Hope this helps.