What if I built a bench with a weight scale and laser points to measure reps? Little pads to put dumbells on and calculate the weight and some kind of device for them to measure reps that sticks on with magnets?
Then it could all tie into an electronic device and give you a journal of your workout with out needing to stop and write it down.
You stack your weight on, hit calculate and it saves that weight. Start a timer then you do one set and it calcs reps, calc rest time, second set reps, rest, etc.
I could sell this to gyms they could hand out the devices to customers and the customer could then come back afterwards and either have the gym transfer it to digital media or print it out for them.