I've spent a bunch of time over the past month chasing after power (meters). Priorities:
1) Use it on tri bike on trainer.
2) Use it on road bike for rides with the local Roadies.
3) Use it on tri bike in races.
I chased after a lot of ways to skin this cat. Any solution needed to do ANT+. My stationary trainer already does power, but that didn't help me any with 2) and 3).
The cheapest way to get power is a used Powertap wheel on ebay. I got one for $200. So that's a solution for 1) and 2) that allows me to sell the expensive trainer with power and I can go back to my no-frills trainer.
I still hadn't solved 3) tho. It looked to me like a power crank solution was the way to go, unless I wanted to swap my old disc out for a disc with a Powertap hub. I found the latter on ebay for $1k which is a pretty good deal. But my old disc is so beat up that I wouldn't get hardly anything for it so the ultimate cost of the swap would be high. The crank solution wasn't infantry simple either. My bike used a BB30 bottom bracket which excluded a lot of possible crank power solutions. Also, I further limited the # of cranks that would work because I wanted to put Rotor QXL rings on the tri-bike.
Ultimately I found used SRAM power crank solution being sold by Amazon. Some kind of NIB that was returned to them, and is a BB30 and compatible with QXL rings.
Lessons learned.
-Used Powertaps deserve a look because they are available cheap. Some are old models tho, so know your Powertap model #'s.
-A Shimano BB and/or crank makes life easier because so many crank power solutions are compatible.
-WatTeam has an interesting DIY solution for $500. Limited crank compatibility now, but carbon cranks are supposed to be added to the compatibility list soon.
-Call up power crank mfrs and ask them about cosmetic blems that might be available.
Books @ Amazon "If only he had used his genius for niceness, instead of Evil." M. Smart