This is a tipping bucket mechanism that can be fitted out with a few small, round magnets and a reed switch or Hall effect sensor to count the tips. It is designed for measuring hydroponic nutrients but has other uses.
As the bucket fills, the centre of gravity creeps towards the pivot until the whole thing suddenly unbalances and dumps its contents. Now empty, the bucket's centre of gravity is once more to the rear, and so it tips back again, ready to receive more liquid.
A video of one in action being controlled by an Arduino can be seen on YouTube here http://youtu.be/EZ2_Gmmt1ww
Put small, round magnets in the cavity in the handle. One on top will hold one in from below. By adding more magnets you can increase the amount of liquid the bucket will hold before tipping.
The holes in the frame can be used to mount to mount the mechanism on a wall.