yeah it's called a drum trigger or brain

try a second hand Alesis D4 and work your way up from there

.... or you could process recorded track later using Drumagog plugin

I assumed he was on a hardware multitrack drum recording setup

Groff is correct
if you are already in the computer, there are a few drum replacement and drum triggered software packages out there

If the snaretrack is unprocessed you can use a D4 or ddrum also on the output of the snaretrack if already in the computer. They have very nice sounds also.

I use Sound Replacer. It's nice for replacing and layering drums. It's not realtime though, definitely and Audiosuite plugin.

Cheers,
-Ryan-