Also keep in mind that Google is now doing automatic scans of all apps that you install, which is quickly making 3rd party antivirus apps superfluous. But those antivirus apps often have some nice antitheft features that may be worthwhile. I use Lookout, which will take a photo with the front facing camera if someone unsuccessfully tries to unlock the device 3 times in a row. Lookout will then email that photo to you, so you can see who's trying to unlock your phone.
Posted via Android Central App--please excuse the brevity and any typos!