If a little finger crank could charge the phone, I'd be able to run my house with a dynohub. Heck, I could arc weld with it on the last descent of my morning commute.

The ideal would be to add in some control to allow dialing the output (and thus resistance) up and down; max it out for regenerative braking while bombing down a hill with a stop sign at the bottom, but minimize it for climbs or sprints, while manually finding a happy medium in the flats. The battery could level that out a bit for the devices, especially if using a larger pack outside the hub, (and that's probably the only way you'd get practical use out of 1-2 minute shots of regen braking power) but I still like the idea of having a couple minutes of bare minimum power storage integrated into the hub so that feature (not having the devices switch out of charging mode at a stoplight) is always available.