You can buy power grips alone or with pedals attached.
I bought mine alone and attached them to my existing pedals, so I can't speak to the quality of the peds sold with them. They will work with any pedal that can take clips and straps. Very easy to install and adjust.

I've never had clipless pedals, so I have no idea if they're equivalent.

Personally I'm very happy with them. They are easy to get into and out of. They give you more power in the pedal stroke and that "attached to the bike" feel, but still leave your foot room to move around on the pedal. I can wear any pair of sneakers I want with them and that's a big plus, especially if I'm riding to a destination where I'll want to hop off the bike and walk.