For us geeks would be if the little "signal" logo on the mobile screen would change from $ to $$ to $$$$$$$$$$$$ as the cell gets more congested and the data packets get more expensive.
This would allow me to pay top dollar regardless of price if i really need it (or to pissed to notice), or opt to not surf it it gets costly when it's not so important.
You can have my idea for free, vodafone. Just send me a 1000$ pre-paid SIM sometime in return for the favour, thanks. Ah yes, and throw in a nice Android handset please.