The Garmin based system hasnt been releaced on general sale yet due to issues with robustness. They are being used on pro bikes but they only last a few months at the moment.
This has been pushed out to Q1 2013, possibly Q2, according to the Garmin earnings call last week. Polar offer a Keo power pedal as an alternative, but this uses a proprietary communication protocol (W. I. N. D.) and thus isn't compatible with anything other than two Polar cycle products - even their triathlon offerings do not support the necessary protocol.
In short, until Brim Brothers get their act together, you're left with a choice between wheel (racing or training, pick one) crank, or hamstrung pedal based system. I was hoping for Vector to arrive before Christmas, but sadly no joy.
If you opt for crank, the lower end of the price spectrum is occupied by power2max, who've been going for a couple of years now and seem to get pretty good reviews. All communication is ANT+ and the units are supposedly pretty accurate (and you can calibrate and zero them at home). SRM are the gold standard still... but if you're going to splash out that much you have to ask if it's worth the extra £1k+...
Edited: 05/11/2012 at 16:47