There were cell phone based payment systems before iPay, but now the point of sale terminals are going to finally happen. I think apple Pay is going to be a huge money maker as it becomes wide spread. It's timing is interesting. Credit card makers in the US are on the cusp of rolling out chip and pin and merchants will need to upgrade their point of sale terminals. . No one is excited about this mandated cost since analyses have shown didn't change the total amount of fraud (in the long run), it just shifted it from in-person fraud (where the chip works) to internet sales. However, apple pay, which does work, can just slip stream right along on the mass pos changeover without imposing an extra cost the merchants were not going have to pay anyhow (for chip and pin).
Second, this year at least, apple appears to have the best finger print reader. As motorola noted recently they left finger print ID off the new nexus because all the other vendors of the technology produce unsatisfactory finger print ID. It's either too many false positives or too many false negatives.
The challenge to apple pay of course is the market share of handsets. But as long as there are enough to make it worth making the NFC sensors compatible with Apple's bank authorization schema they will be in stores, giving apple a growing drip feed of cash.