1. Micah Elizabeth Scott built a working RFID tag using just two parts: an ATTiny85 micro controller and a small inductor. The two leads of the inductor are soldered directly to two I/O pins of the processor.
That is the only connection to the processor. The power and ground pins are not connected. The processor gets power via leakage current from the I/O pins. It gets clocked from one of those I/O pins, too.
https://scanlime.org/2008/09/using-an-avr-as-an-rfid-tag/
2. Here's another one of hers, this time with a coil made from magnet wire, and with fancier mounting. The coil, processor, and this time a couple of tuning capacitors, is squished onto duct tape and sealed with clear packing tape.
https://scanlime.org/2011/05/duct-tape-rfid-tag-1/
3. Trammell Hudson made use of her antenna and processor only design for a project of his, which has a pretty good write up.
The ones described in the video are UHF (860-960 MHz) RFID tags, which differ considerably in design and protocol.
