A new remote locking feature just appeared in the Android Device Manager. Users running Android 2.2 or better can now lock a lost or stolen phone, even if it's in use.
The new functionality asks you to enter a PIN that will unlock your phone once it's found — Google recommends you use something different from your current password, of course. If your phone isn't on a Wi-Fi or mobile network, the lock command will wait until a connection is established, and a full remote wipe remains as your last resort. [Android Police via Verge]