It would be great if you had more info about compatible GPS units. Are there specific brands/models that work? Are there keywords to look for (any XYZ protoco

It would be great if you had more info about compatible GPS units. Are there specific brands/models that work? Are there keywords to look for (any XYZ protocol-compatible GPS)? I saw mention of the Garmin 605 and 705 in the FAQ, but are those the only models?