Are there any lap counting devices available?

Are there any devices on the market for counting and displaying lap number
as well as split or lap times? I'm new to the 'masters' swimming scene and
I find there's so much going on inside my oxygen-starved brain that I
often lose count in long sets :)  

I was thinking of some inexpensive electro-optical device that you could
attach to the lane lines a few feet out from the wall and the swimmer's
body would break the light beam when it passed. The underwater display
would be trickier - perhaps some low voltage LED/LCD or maybe we have to wait
for E-paper to arrive. Maybe there is some sort of fibre-optic way of
displaying the times - maybe too expensive.  

Thanks