Chinese gadget manufacturer Ajoka offers a spy belt buckle with integrated digital video recorder.

In the early days spy cameras had a secondary large unit that housed the recording. In the very, very early days that was a VHS recorder. Now with the advancement of flash memory, the spy cameras can directly record video footage.

The Ajoka Buckle DVR measures 2.54x1.47x0.60" and is supporting microSD cards from 128MB to 2GB to store video.
The belt buckle shoots video in 3GP video format with 176x144px resolution and 15fps. It also records audio of course with the integrated microphone.
The battery life of the spy camera belt buckle is 3 hours. It can be charged via USB.

Given the position of the camera lens, You have to 'get lucky' to actually get a face on video.

The whole sale price is about $150 for the Belt DVR.
Via the Ajoka site