You can activate German ID cards to work as RFID smartcards for online identification. Practically, there aren't all that many places to do it, and not many people do so. You also need a smartcard reader, but those were available reasonably cheap (no idea if a smartphone with NFC can do it or not)

(You also can have a certificate on it, but they missed an opportunity and didn't make it default, you have to ask for and pay extra for that. Would have been a chance to widely roll out certificates of the standard necessary to legally replace signatures, instead of other crap that has been proposed as a replacement sigh)