Avast Anti-Theft-
Avast Anti-Theft - Android Apps on Google Play
I'm using Avast Anti-Theft because
it's free and it has more features than the standard Android Device Manager. I can white-list SIM cards, and I can also lock the phone via SMS and I do get a notification if the SIM is changed.
The impact on the battery life is low, and the Avast page from which you can control your device is very well structured and easy to understand.
I've been searching for a better FREE anti-theft app on but I cannot find one, so I'm using this app for about a year or so.
Also I would recommend that you encrypt your phone -
Encrypt your data - Nexus Help
Avast Anti-Theft Features:
Remote Listening
Remotely have the phone call you elsewhere, with screen blacked out, so that thieves cannot see the call status and you can listen to the phone's surroundings.
Siren
Activate a loud siren which reverts to maximum volume if thieves try to silence it.
Trusted SIM Cards List
Establish a 'white list' of approved SIM cards that can be used in the phone without triggering a theft alert, or easily set only the primary one in the phone as ‘trusted’.
Stealth Mode
Once enabled, the app icon is hidden in the app tray, making it 'invisible' and thus difficult for thieves to detect.
Remote Locator
Remotely locate phone via GPS, Wi-Fi, or mobile network – for maximum accuracy. Can locate either once or continuously.
SIM-Card-Change Notification
If stolen, and a different (unauthorized) SIM card is inserted, the phone can lock, activate siren, and send you a notification (to your Avast Account) of the phone's new number and geo-location.
Remote Memory Wipe
Remotely trigger a full, permanent wipe of all phone data (e.g. contacts, call log, SMS/MMS, browser history, apps, email accounts), including reliable, physical wipe of memory cards (limited functionality on older versions).
Remote "Lost" Notification
Remotely send a "Lost" command to trigger same actions as SIM card change (e.g. phone lock, siren, or USB lock). "Found" command deactivates "Lost" command.
Remote History
Query the call log, contacts, and SMS messages remotely (with each forwarded as a separate SMS message, but able to be filtered).
Remote Restart
Reboot the phone by SMS command, which will lock the phone by asking for the SIM card's PIN code. (Works only on rooted phones.)
Low Battery Notification
Phone is able to send low battery notification to a secondary device.
Remote Lock
To protect your data, your phone can be locked remotely and unlocked only with your
password.
Remote Settings Change
All of the Anti-Theft settings can be changed remotely.
Message the screen
Send a customized message to your phone display (e.g. with a reward for its return), whether it is locked or not.
Lock Phone Settings Access
Enables remote locking of the phone's App Manager and/or settings.
