Garmin Xero, or Magnetospeed Sporter if you're on a budget. With the Garmin's release, the Labradar and Magnetospeed V3 have become much harder to recommend.
For the most part, I wouldn't bother with the rest of the market if they we free, I don't trust their accuracy enough.
For the most part, I wouldn't bother with the rest of the market if they we free, I don't trust their accuracy enough.