How could be a wireless ~20m checkpoint device ??

Hi to all experts,

Arduino is a very easy-friendly microcontroller than I'm learning step by step and it was helping me to flow my imagination.

in this case, I'm trying to make a wireless checpoint (timer checkpoint) with a range of 20 meter aprox. but I don't know how can be done, and the sensor could be a electronic device... the power energy and weight is not important cuz will not count persons or something.

so for example, arduino will have some antenna in a X point of a way, then some car or byclcle will have the other part of the electronic device with an ID on it, so when it passed fastly in the range of 20 meters over the arduino antenna, it must register the time were it passed and the ID of the device.

so, some idea of with how can i make this? xbee what the range? if it passed very fast will work?


Once you get beyond a few meters you probably need active RFID tags like these:

The long-range vehicle tag can be read at 300 MPH up to 183 meters away.