Well, I just received the force sensor and driver board that will be used for the band measuring project. Next, I have to select a robotic motor for the band stretcher. If this is too far from a slingshot post let me know and I will be more reserved with the progress of this project.
I've been tinkering around a bit with Arduino myself recently. Just a newbie side hobby and never imagined applying it to slingshots (got a pretty spiff binary clock in the works at the moment though!). This is very cool. Really looking forward to your next update!
Happen to have a link to the force sensor you bought?
The aluminum bar looking thing is the actual sensor, sometime called a load sensor. The one here is 1kg max and was purchased on amazon with the driver board for $18.95, I am thinking I'll be using a 10kg sensor instead, otherwise I'll use leverage to reduce the load of the slingshot rubber by 10x. I'll post the arduino software I write and the supporting libraries I used to test it on GitHub and provide links if you plan on using one.
Here's the link to the sensor kit:
Here's a link to my github for reference, but the code has not been posted yet: