Detecting an Individual Entering and Existing a Room

Using Arduino Project Guidance
1

I'm looking to play a practical joke on a colleague and trigger a sound upon him entering his office, and then a different sound upon him exiting. My initial plan was to somehow plant something on his person, like in his wallet, and then use a sensor to track him through the doorframe. It has to be a sensor on him, because I do not want the sound going off for other people that venture through his doorway. I've seen a ton of RFID-based door openers, but those require extremely close proximity to the tag.

Any suggestions on the type of sensor/tag I should be looking at?

2

I'm looking to play a practical joke on a colleague and trigger a sound upon him entering his office, and then a different sound upon him exiting.

But, I'm not going to bother searching for all the other people that have tried to do the exact same thing.

Any suggestions on the type of sensor/tag I should be looking at?

Growing up?

3

Wow, tad rude there :(.

Any number of sensors can be used to do this. Here are some ideas that should prompt some searching.

Detect when the door is open. Burgalar alarms use these magnetic reed switches to do this.
Detect proximity to an area. some sort of distance sensor.

Pads on the floor. (this can literally be as simple as two bits of tinfoil that connect when they are pushed together.

4

The OP wanted to distinguish one particular person entering/leaving the room, not just anyone entering or leaving.

5

colleague and trigger a sound upon him entering his office,

Who else would enter his office whilst the electronics are setup?

6

Any suggestions on the type of sensor/tag I should be looking at?

Solution 1: you can hire a dude for that. A picture + minimum wage required;
Solution 2: you can implant some sort of rfid into your friend and put sensors around the room. Kind of like proximity sensors in some cars.
Solution 3..n: when everything failis, go to Solution 1.

7

Who else would enter his office whilst the electronics are setup?

I give up, what is the answer?