put a cover on their iPhone that they can put their NFC card into and use it that way
Terminology clarification: If it's in a card, it's not NFC, it's a "contactless smart card". NFC is, specifically, a variant of the contactless smart card protocols embedded in a larger, battery-powered device. It does emulate a contactless smart card, which is how it enables payments, but it does a lot more as well. NFC devices can also act as smart card readers (note that "reader" is something of a misnomer; it's just two computers talking to one another) and they can also act as RFID tags or readers (or writers, for tags that are writable).
This broad array of capabilities, BTW, just highlights how unfortunate it is that Apple is limiting it. In Android-land, not only can you use NFC to make payments (Google Wallet, whatever the ISIS Wallet has been renamed to), but there are a lot more uses:
1. You can download one of many smart card reader apps (or write your own) and use them to read any contactless smart card you have around, including many payment cards. What you can see depends on the security protocols implemented by the card, obviously, and also depends on whether your app knows the right commands to send. If you like you can buy your own Javacards, program them, and write your own app to talk to them, to do whatever it is that you'd like to do.
2. Most of said smart card reader apps also support reading and writing RFID tags, which you can buy inexpensively. Many people have come up with uses for these, such as automatically changing phone configuration (volume, etc.) when a particular tag is scanned. My Moto X offers the ability to register an RFID tag as an unlocking device; whenever I scan one of the registered tags, my phone unlocks.
3. Ever since Jelly Bean (IIRC), Android has used NFC as a method to initiate device-to-device data transfer. On several occasions when my wife and I have been driving separate vehicles to the same location, I pull it up on Google Maps, tap my phone to hers and touch the screen, and then it's on her phone. You can transfer pictures, files, and anything else apps care to support. NFC isn't actually used for the data transfer to avoid having to hold the phones together for a long period of time, but it identifies the pair of phones that wish to do the transfer, which is then carried out through Wifi or mobile data.
... and more. Here are some more concrete examples of clever uses to which people have put Android's NFC capabilities: http://trendblog.net/creative-...