Medtronic's SynchroMed programmable infusion system now has a patient-controlled option. The new Personal Therapy Manager allows patients to self administer pre-prescribed pain medication during episodes of increased pain (press release).
There is no data that I can find describing battery life or the wireless
radio link between the implantable pump and controller. Surprisingly, a
component diagram of the pump doesn't even call out the radio (you can
see the diagram here). Perhaps they're using MICS, the medical implant communications service (more here and here).