Compact Human Motion Sensor with Built-in WiFi Signal for Laptop/Mobile Detection

Hello
I'm designing a project and i need a sensor that can detect human motion.I would like to detect the output signal of this sensor by searching it via laptop or mobile phone as if they are searching for a wifi signal.
I would like to know if such sensor is available or should i build a module for this using several components?I want this sensor to have small dimensions so it should be carried by the user anywhere.

Awaiting a reply.
Many Thanks
Ayman

You could try a Pir sensor and connect with a processor to a usb.

I would suggest an accelerometer. A PIR sensor would be more about other people's movements (because it will be worn by the person using it). If there are no other people around, then sensing movement (i.e. movement of the User) would rely on temperature differences in the surrounds [still might work, but unreliable].

But, to make it portable/wearable, you would have to come up with a power source that was small and light and able to run a WiFi transmitter for a reasonable period of time (and not be toxic to the wearer). I doubt if present technology is up to that. I see that as the "game breaker" in this project.

I suppose it would be possible to fashion a generator that would convert the persons motions into power--but, I still don't think there would be enough energy to power a WiFi transmitter.