If you're paranoid about losing both your smartphone and your tablet... well, you probably shouldn't be carrying both in an area where either is likely to get stolen. But if you do, and feel like you need an extra layer of protection, McAfee is here to indulge your fear. Smart Perimeter Plus (in the Security Innovations app) links your Android phone and tablet, then sets off an alarm if either are separated from the same WiFi network. It's a free download for devices running Android 2.1 or later.
The concept is pretty simple: connect both your phone and your tablet to the same WiFi network, then pair them with the app-specific PIN.