Which type of arduinos or microcontrollers support all of your sensors and are the most small and compact in size we can get. (This is for a wearable technology project). Each microcontroller would support one sensor and send its data through zigBee. Also, how would we know how many pins each sensor takes/needs?
Thanks in advance.
Any system with analog inputs and (preferably) 3.3V operating voltage should do. Perhaps one of the smallest you'll find around is the Arduino Pro Mini, although we don't know the full IoT / micro controller boards ecosystem in detail.
Each sensor can take up to 4 pins, although you should be able to do the trick with only 3 (VCC, GND, SIGNAL); the 4th pin is used in sensors like the EMG and ECG for the mid-point voltage, however you can create that voltage on the sensor board with voltage divider based on through-hole resistors.
A couple of picture on how to create the mid-point voltage follow in attachment.
The BITalino Team