I don't see how an NFC/Bitcoin implementation is a bad idea.

For the right price, it could replace the smartphone as the Bitcoin tool of choice for day-to-day use.  Given that everyone with an iPhone has trouble using Bitcoin today, this can only be a good thing.

Add encryption, and a safe private-key backup so you can take back the funds as soon as you realise the NFC card is lost and I think you have something that could be quite useful.