DART just launched a new service that does exactly this. 4 zones launched today, but many more are coming throughout the year. Try out planning a trip in the updated GoPass app and, depending on where you're going, you should see options for GoLink.
I'm in Allen which is outside of the DART service area, though, so I'm probably not covered. Although I'm just across the Plano-Allen border. Maybe I could just walk a couple blocks south and summon a ride. :D
Thanks for the info! I'll definitely check it out.
