When I bought them, I think they were called the K&K Pure Westerns. They are three sticky piezo pads that attach to the bridgeplate. They are passive and I wanted them that way because I didn't want to attach any more electronics to the guitars than I had to.
I've used a Fishman Rare Earth soundhole pickup, too. It sounds great and I would love it if I had a guitar it could live in full time. The sound wasn't as "acoustic-y" as I wanted but it worked well for fingerpicking. It also means giving up the body sounds. If percussive tapping is part of your thing, that might be a problem. Of course, it might also be a good thing.
I had a PADI because everybody told me they were awesome. It is a good piece of equipment but I didn't like how it matched to the K&K. I ended up rolling the bass all the way off. Then I tried an Ultrasound and it did everything I wanted from the PADI and was simpler.