anyone using these?

https://www.urbanbiketech.com/about_solidaxle.html

seems like a cool thing to keep thieves from going at your wheels, kind of pricey though. anyone got them on there singlespeed/fixie?

I have them... they are bulletproof and the most secure wheel locks I've seen. grinding them off is the only way to defeat them and would risk ****ing up the bike. If you need the security they're worth the extra price.

dont you need 15mm for track hubs?

no, you need a nut that is 10x1 (rear) or 9x1 (front) (except campy et al).. looks like they only sell nuts for rear wheels..

I'm guessing a chain tensioner would be a good idea for these, right?

If I'm not mistaken, pitlocks can be pretty easily pinched flat and unscrewed with hand-plyers.