technology to search small objects like pendrive, key-chains etc
There are a few commercial devices to find lost remotes, keys, and other small items. They usually work by having a small radio frequency (RF) receiver that uses a button cell and attaches to the item intended to be found. (It's similar to a keyless entry fob for your vehicle.)

When the item goes missing, the user presses a button on a base station (or sometimes another remote-size thing; which I suppose could also get lost, but that's another subject...). When the receiver picks up the signal, it emits a beep and/or flashes a light, etc.

Bluetooth is only designed for about 10 meter (30 ft) range, but higher power Bluetooth devices could have ranges up to 100 meters (300 ft).

Some commercial products that are similar to your need:


KeyRinger
Click N' Dig


And a discussion about a device that might respond to sound instead of RF:


  http://forum.allaboutcircuits.com/showthread.php?t=41323