So I moved into a highrise and was given a card for entry access. However, other residents seem to have a little round plastic dongle on their keychain and press this up to card reader instead.

Where do I get one of those?

Both the card and the dongle contain a little RFID chip with an access code in it. Technically the data can be read and written to any other RFID chip using a reader/writer. So if everyone else has a blue dongle, just walk to the management office and see if they have any dongles with the same code, or go to a place that writes RFID data.

You could even write it to the RFID chip in your phone and open the door with your phone. In theory at least.

Thanks, went and bought one from the wuguan for 30rmb. They are blue like you said.