For me, one of my favourite apps lately has been Cerberus Anti Theft https://play.google....sdroid.cerberus
Granted the name might be a bit misleading as no app can stop your phone being stolen, however this could easily help you get it back. It has lots of useful features through the website once the app is installed, like taking pictures or recording audio without the thief knowing and allowing you to download those items through your email, and also locking the device with a pin, tracking with GPS (which you can enable within the app) and you can also reboot the phone (if you're bored enough, can do this continually to pee off the thief) and you can also wipe the device and SD card if things get drastic.
A licence for up to 5 devices simultaneously costs just £2.49 as well. so it's a bit of a bargain.