I've been asked to develop an app with the core functionality of reading RFID chips in pets and checking those identification numbers against a database through some web service.
I was first directed towards iCarte, supposed maker of an NFC/RFID Reader accessory for iPhone. I sent them an email that was immediately returned due to them exceeding their mailbox quota, so I suppose they are out of business?
Other solutions come in the form of Bluetooth ready readers, like those from Serialio. Demos show data being read into iOS's Notes app or some grid app. I haven't developed iPhone apps in a while... is the Bluetooth API available? How about for Android? Could I read from the Bluetooth reader straight into an app?
What other options are there?
Before you start any work please familiarize yourself with this:
http://en.wikipedia.org/wiki/ISO_11784_%26_11785
and this: http://en.wikipedia.org/wiki/ISO_14223
RFIDs for animals are completely different protocol than NFC. It is more like UNIQUE tags (125kHz) . Anyway above ISO standards will be a good starting point for you.