The range of NFC is about equivalent to (usually less than) the low power RFID options. I mean this can all be solved if you guys wanna dish out an additional $180 for UHF equipment lol but I figure that's too much. I would only pay that much myself because I have a personal interest in technology and would like to experiment with it, but for this project I need to keep cost down, especially for the sake of all of you. My goal is to be able to have a parts total of under $100, a mere 20% of the typical cost of a (decent) retail system.
You would have to either keep your phone charged, plug it into the vehicle, or just use the key. I don't plan on completely eliminating the stock key cylinder, just moving it to a place that's more out of the way, just in case.