Some phones have poorly designed antennas. I bought PN532 units with external antennas and they work wonderful. I agree with the others, inflammation does prohibit utilizing the implant.
If you plan on developing NFC technology then get a stack of NFC cards. The Dangerous Things android app can be used to pre-configure the card. You can then develop from there, this will prevent you from locking yourself out of your implant.
PN532 with external antenna product page
https://www.elechouse.com/elechouse/index.php?main_page=product_info&cPath=90_93&products_id=2271
Image of the new PN532 with external antenna
I’m working on an open source project which will allow people to take the external antennas, mount them on the door frame, store the rest inside the door or wall for use with NFC badges/keyfobs/implants.
Best regards,
Connor Goodwolf