develop webcamera with battery and memory to SELF RECORDING (Disc Processing System)
This camera module is only 6 mm \$\times\$ 6 mm, so it should fit in any device. 



It has an 8-bit parallel interface for data, plus an I2C interface for control. Just 10 dollar.

For the storage you may want an SD-card. The requirements for the microcontroller aren't that high: all it has to do is capture the data and pump it to the SD-card. This entry-level Cortex-M0 controller can run at 50 MHz and can easily handle the data throughput.