Not much right now ... but using your mobile phone as a credit card is coming soon, in which case they could be worth ... who knows! Depends on how well it takes off, and whether the technology is known as 'Mobile Credit Card' or not.
Might be worth mid xx if you want to sell now. But I'd hold on to them for a year or two.
binaryman, that domain (walletphone.com) is going to be very hot very soon. the japanese already are testing it, and its bound to be mainstream in US and other places soon. keep it and get a good price for it, if you sell.