I'd like to do some test, I have here 2 types of sonic sensor... A parallax ping and a cheaper i2c SRF02. Probably I will wait for warmer days, as here in Italy for our standars 
it's still cold I like your project a lot!
I'd like to do some test, I have here 2 types of sonic sensor... A parallax ping and a cheaper i2c SRF02. Probably I will wait for warmer days, as here in Italy for our standars it's still cold I like your project a lot!