I have a little question regarding my watermeter. I was looking for a way to monitor my usage however its no digital meter only a row of numbers turned by a mechanical water-wheel
Example:

Window:

So first I tought some fancy OCR with rpi cam noir
However after some research I found out there is a hole where you can put in a hall or reed sensor and sense the pulses generated by the waterwheel.
Example:

I found this sensor:
https://www.flukso.net/content/water-probe
But the price seems steep for this kind of sensor and I don’t know if this would work on a rpi since this is for a proprietary system.
Does anyone know what type of sensor and which model this is and or where to buy it in europe ?
Thanks in advance,
Xtremegamer