Speed Sensor

The Weeling Project requires to capture the Rear Weel and Front Weel speed (rotation per minute), therefore I had to think about a method to sense them.
For the Rear Weel, there is no problem , since the bike alreay have a dedicated sensor that goes into the engine control unit (ECU), so, I just need a pick-up and a simple signal conditioning circuit: I think a 100kOhm and 2 diodes as protection circuit for the uC input would be enough.
About the Front Weel speed I plan to use an Inductive Speed Sensor as shown:

It must be mounted as shown:

How it works:
The Inductive Speed Sensor sense the metallic bolts closing each time they comes closer. It is recommended to lave 2mm dinstance between the sensor and the bolts. The nice stuff is that the sensor has a LED on the back-side, so, each time it sense the bolt it also display it.
The sensor has 3 terminals: Vcc, GND and one output. The sensor is NPN, so can be connected in common emiter circuit configuration.
In the next days I will start to play with it and I'll try some input circuits.