A small device that fits into older phones in the same slots as car kits do, but just slots nicely into the bottom of the phone (so the phone just looks 1cm longer).
When the phone rings .. a signal is sent through to the small extra bit of plastic (thinking its a car kit) -- the small device then
plays your choice of amazing, new sounding ringtone you've chosen using buttons on the kit..
Everyone thinks you've got a top-of-the-line phone, where as in reality the extra 'ringtone' gadget only cost you $5 from the market rather then the $380 the actual entire nokia TX6000 phone would have cost you!