Talk is cheap, unless of course you actually hire Kathleen Turner or Meg Ryan and they aren't already fanatical Segway owners. The current i2 might even be capable of speech. It has some sort of annunciator in there to allow it to beep.
I once rigged a portable device with speech using the piezo beeper to tell the top sales dude "Scotty told you this feature wouldn't work." Of course he got the last laugh because after that I had to add all kinds of voice to the device as customers fell in love with it.
The rapid charger would be an accessory. I'd design it to plug into the same AC port. Cost to the base Segway would be less than $1.
GPS: dealer option. Ditto, if you want it, you pay for it.
Cigarette lighter. You got me there, that might add $10 or $15. Especially if it actually came with a lighter.
Not having to carry a battery pack for the head light and Macarena air horn: priceless.