Appenzell itself will not consume 3 days, in my opinion.
There is certainly enough to do if you use it as a base for day trips.
There is some nice hiking in the hills around the area, and over toward the Bode and along the Rhine.
map.geo.admin.ch/?topic=ech&lang=en&bgLa yer=ch.swisstopo.pixel karte-farbe&layers=ch.bav.ha ltestellen-oev,ch.swisstopo.swiss tlm3d-wanderwege&layers_visi bility=false,true&E=27 50523.69&N=1249242.84& zoom=5
map.wanderland.ch/?lang=de&route=all&bgLa yer=pk&resolution=100& season=summer&layers=W anderland&E=2748407&N= 1242250
Once on a jet lag day we rode out from Zürich, had a nice lunch in Appenzell, then walked an easy and pleasant trail to Gais (7 or 8 km) and took the "train" to St. Gall then, rail back to Zürich.
You can visit Säntis and the Seealpsee, as well as Ebenalp --
And, across the "Bode" ( der Bodenseee, Lake Constance.) ,
the Zeppelin Museum in Friedrichshafen is worth the trip.
You could explore the Taminaschlucht.
www.schweizmobil.ch/de /wanderland/routen/rou te-0937.html
The restaurant in the restored building (Altes Bad Pfäfers) which held the thermal baths is pretty good. Their wine list includes a pleasant Müller-Thurgau white from a nearby vineyard....Portaser is the region name, I think. It is from from Weinbau Burghof ( Robert Schwitter) the highest vineyard in the region ( but not in Switzerland). I'd not seek it out because it is nothing special....unless they have the Auslese. That has a lot of character and is worth getting, when they have it.
And, of course, St Gall.
Check this thread, which should have a few more pictures in the next week or so, if I can get to it befre I go to Switzerland in late May.
www.myswissalps.com/fo rum/topic/activities-in-st-gallen#hRjtxaDW9mqS6v8 AAFcRTQ
I don't know how much territory is covered by the Appenzell card, but I'm guessing that some of those things will not be covered.