[Terr_]

I'm imagining:

1. User defines a "multi-location" spec, like "MyFastFood" as "Having [2] or more of [Fast Food] excluding [Taco Bell,]"

2. User defines a requirement for their heat map which references the multi-location, ex: "Within [30 minutes] to [walk] to [MyFastFood]"

3. Within the context of a particular [user's requirement] and broad [city/town/region], a 2D area/gradient can be generated, and cached for a rather considerable period given how slowly businesses open/close.

Granted, that's the ambitious version. A simpler one would be to not support "at least X", and to combine the multi-location and the distance-rules all together into a single condition.