The units I know of are:
The Garmin Edge and Forerunner.
The Basic Edge is the 200 (b&w bread crumb mapping no sensors.
Edge 500 is the same (b&w) but take sensors for HR & Cadence. There's a similar 305 (I've got one) but I'm usure of availability.
The Edge 605 and 705 are full colour, detail mapping versions of the above (605 No Sensors, 705 Sensors),
The latter one or two have been superseded by the 800 which is the all singing touch screen version.
I don't know about the Forerunner models but they are a watch like unit.
Bryton and Holux do budget alternatives.