My first: mid-'90s, Garmin 'GPS II Plus' B&W "hiker's" (no inbuilt charts, key in your own waypoints and routes between them) GPS. I carried on flying with it thereafter. It was small enough to fit (velcro'd) on the coaming. It displays a narrow 'highway' with centreline representing the planned track, or (if too far off it) the direction and distance to go to regain it. It was ~10 years later before I had a first tablet and got a SD subscription for it. Ironically, the syndicate RF6 in which I first used the Garmin had a built-in Decca 'rolling map' display from early '80s. One of our members (Smiths Industries avionics engineer) had 'liberated' it from the company scrap pile when Decca chains started to be withdrawn worldwide; he had originally fitted it to a RF4, which was thus, then probably the motorglider with the most sophisticated avionics in the world
Even without any Decca inputs, its inbuilt accelerometer system gave a reasonable estimate of distance and azimuth from 'starting point', ie where it had last been switched on.
Smiths was making (and widely exporting) mechanically displayed but electronically fed cockpit moving map displays from '50s. The one in the JAM Trident often attracts visitors' attention.
(mere guide at) Jet Age Museum, Gloucestershire Airport
http://www.jetagemuseum.org/TripAdvisor Excellence Award 2015
http://www.tripadvisor.co.uk/Attraction ... gland.html