remember what RFID stands for
(Radio Frequency Idenification)
Basically, all they do usually is broadcast something (like a price, or brand name, etc...)
All an RFID sensor does is sense and READ these tags. End of story. (usually a 2 meter range if I remember right)
So putting in a motion sensor onto an RFID sensor would create a RFID sensor that tuned on when someone came with the set range... and read any RFIDs on them.
which would still do what you want it to.... Kinda. Everytime someone walked past the door, you would get spammed with advertisements from the RFIDs on the person ("Ask me how much I love my Carbucks Soykaf!"... "As you can see, only REAL men wear Stanfields." ..... "Have smooth and sexy legs forever with Renraku's new Hair-be-gone lotion! use only once a month for sexy, silky legs for 30 days!")
Conversely, use the motion sensor could be set up to send a tone to your commlink that would alert you to the presence of someone near the door. Just Keep in mind, these sensors are not invisible. Small, yes... tiny even... but they can still be noticed. (based of the reduction in size of motionsensers I have seen in the industrial field.... by 2070 they are probably 2cmX2cmX3cm.....about the size of quarter... and as tall as 8 quarters stacked.... so small)