I am trying to find out for certain whether the new speed/cadence sensors are compatible with the FR 610. Garmin's site as well as some other sites only list the FR 620 but I have seen some that say the FR 610 is as well. If the FR 610 is not compatible with the new sensors, would it be compatible if only the new cadence sensor was used (and GPS was used for speed)?
According to this post on dcrainmaker.com, the 610 is not compatible with the new sensors. Ray has a lot of experience with these things, so I'd trust what he has to say.