Does instant e-mailing price checking service exist?

theowl_2

What I mean is, does a website exist in which you can enter a product and have them e-mail you when prices drop below a level you set?
I know travelocity do this for flights and maybe Argos I think, but does anyone know if there is a website that will trawl through all the prices daily and go a step further than shopbots such as Kelkoo and actually e-mail you when the prices drop?
It would be very handy and time saving, as sometimes I will not pay more than a certain amount for a product and have to keep checking shopbots to see if the prices drop below my limit.
I am sure this must be available.

Thanks