Very common in the Netherlands (and probably other European countries) for areas that don't see enough riders to warrant a regular bus service. I don't know whether the route planning is computer-driven or human-driven, though.

The big downside of these systems is that you must reserve your route at least 30 minutes in advance, so the bus company can plan the most efficient route. I think they're mainly used by (and exist for) people who have no other options.