While I don't dive as deeply into pipes as I did cigars, I still partake from time to time for the experience.
I have about five currently, with my eye on one or two more. A couple of really nice custom looking cobs on Etsy are pulling me towards a purchase.
Not terribly long ago, P&C sent out an email advertising the Eriksen pipes. The keystones apparently offer a cooler, dryer smoke - though the pipe can be smoked without using the stones..
At $30, it's not a terrible gamble. Just not sure how long a bag of the stones lasts. Those run $10 a bag..though if it turns out to be a 6-12 month investment then that's minimal, and considering I don't smoke a pipe that often and rotate through the few I have, it would probably last longer than that. Also may be even more helpful if the rocks themselves could actually be washed/dried and reused.
Drez, I bought one from P&C last week. It cam with a small tin of stones. I did buy a bag and think it will last months. I've smoked several bowls with it so far. The only thing I don't like is the mouth piece that fits into the stem has a very small hole for the smoke to come through. I tried to put a different stem in it but it is molded just for this stem. Might have to drill out the hole to widen it. On the other hand the rocks do seem to take any moisture out.