Hello I would like to request a predefined ALERT to find your phone. (Of course as part of setup and 1st time use you would want to prompt user for some unique code so not everyone has this enabled by default)

1. If SMS or EMAIL comes in with a specific text, the phone will escalate beep. (optional. Possibly 2 or more levels required. You might want stealth location first before going to setting off all alarms on your phone)
2. SMS and auto-reply EMAIL as to the LOCATION of the phone. A link to google MAPS where the PHONE is located would be very helpful.
3. With the LOCATION information you have, IF the phone is at HOME you can say so. Maybe you left it at WORK. Or maybe the location isn't defined so the above google map would be helpful.
4. You can determine if the phone is moving or stationary. This is helpful if someone stole the phone versus you just left it somewhere.

Of course you would want to enable the necessary changes on the phone to increase volume, enable WIFI, or send an SMS.