Can Android devices with NFC be used as POS terminals for EMV Chip-and-pin cards? I know that Square, for instance, makes payment card readers you can attach to phones in order to make transactions using the mag strip, and they're soon to release a new card reader designed for EMV chip cards, but are these necessary for Android phones?

My understanding is that tap-and-pay using Google Wallet or Apple Pay (or the like) use the same technology and technique to authorize a transaction as EMV chips do. If that's the case, is it plausible that one could create a program that allows the phone to act as the point of sale terminal instead of as the client? If not, please help me understand how these technologies and/or communication methods differ. Thanks!

Edit: I just found out that some EMV chips support NFC while others need direct contact, and that most American cards don't support NFC, including mine.
Most card's chips are readable via the NFC sensor in your phone. There are quite a few apps on the play store that allow you to read card info (ex BankCard Reader). If you are capable of writing your own application you may be able to receive payments via an external API.