I looked into this a fair bit in the past. The Italian sounding 'effeto' (sp) looked the best, and make sure you get the calibrated one - proffessional I think they label it. I have used a couple of the cheaper brands and they were completely hopeless (non-accurate) and snapped my Thomson stem plate at the recommended setting!
If you really want to spend bucks, then Snap-on do a range, but to get low enough for bike stuff it's a digital read out, which I didn't want as I thought the times I would need it, the likely hood is that the battery would be flat! Plus it was £200-300.
I researched into calibration, and the wider the scale say, 0-30Nm the less accurate, than say a wrench from 0-10Nm.
I'll put a link up to the one I thought came out best value with a proper calibration cerificate, and not just a BS certificate that the cheaper one's came with. You'll need to make your own judgement of course.
This is the one I prefered out of the bike specific, but reading the blurb, you still have to request a calibration certificate which is questionable IMO! http://www.chainreactioncycles.com/Models.aspx?ModelID=29422
