Additionally you can consider following sensors:

1. Temperature (Ir radiation)

2  Breathing/ sweat/ ecg detection say

3. blood flow/ pressure

4.One can classify three types of monitoring viz attached to body noninvasively/embedded/ external (eg ir cameras)

5.An interesting application would be crowd monitoring to monitor unusual activities using visible/ Ir / co2 / methane /humidity /vibration/ acoustic sensors.

Good Luck

Cheers

http://www.my-signals.com/

https://www.google.com.pk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&uact=8&ved=0ahUKEwjKrrqssdbWAhXMq48KHSLaCNUQFgguMAE&url=http%3A%2F%2Fieeexplore.ieee.org%2Fiel5%2F69%2F4358933%2F04358934.pdf&usg=AOvVaw0ZKzQBE8EX4yL5wJrkCTaF

Moreover you can use heat sensor (Pyro detectors) PIR sensors 

PIR Sensor

Temperature (Ir radiation),  Breathing/ sweat/ ECG detection sensor, blood flow, pressure sensor.

with this you can use ultrasonic sensor, some bio-compatible sensors are also available.

You can use micro-Doppler sensors if the activity that you are planning to detect is inside a room.

Micro-Doppler sensors. I give you an online link of the available literature.

https://pdfs.semanticscholar.org/fd72/b200146da5b0cf5de329b155ff48fa4e6f14.pdf