Sony is adding rumble support to the PSP, in a roundabout way, courtesy of the DualShock 3. Using the new "PSP Plus" feature in games like Resistance: Retribution, owners of both the PSP and PlayStation 3 will be able to forego the portable platform's analog nub for a better control experience.
By plugging in your AV-output capable PSP (2000 and 3000 models) and connecting the PSP to the PS3 via USB, you'll be able to switch on PSP Plus control through Resistance 2. Doing so adds DualShock 3 control support, letting you play PSP games on your television with a PS3 controller. It disables aim assist in Resistance: Retribution and lets the player alter their control layout to take advantage of the PS3 controller's extra inputs.
The option requires that gamers have a copy of Resistance 2 in their PS3s, but will not require a firmware update for either the PSP or PS3.