We decided to use the pressure sensor instead of vibration sensor.

We collected data on the pressure sensor and built a circuit that will transmit either 5V or 0V based on whether a person is sitting on the bike or not. 

Measurements:

Resistance when no one is sitting on the bike: ~75 to 85 M Ohms. (The reading fluctuates a lot. It sometimes even goes up to over 100 M Ohms. I believe this is because the pressure sensor is best measured when it is straight but because it is really long and light and is moving a lot).

Resistance when I am pressing with all my might: ~1.5 to 2.5 M Ohms. 

Resistance when I pressing my elbow against the pressure sensor: ~6.5 to 8 M Ohms. 

Resistance when I actually sit on the resistor: ~15 to 25 M Ohms.

Next week, we will characterize the pressure sensor.