The Petsafe PCB 102 is a small No bark collar.  It's meant for dogs under 50 pounds. The unit has 6 progressive levels of correction that adjust automatically (resets to the lowest level after 30 seconds of silence). The PCB 102 uses vibration sensor to sense for barking.

It comes in an overmold design that is waterproof.

An interresting feature is the low battery indicator as well has the 6 months battery life.

This unit requires no programming and comes with a Lifetime Limited Warranty.