I do know kids love beeping things, and I'm still secretly trying to make the sales pitch here for you even if nails look like screws and vice versa, so just another idea: might it be useful for the students to count their repetitions themselves (possibly pair-reviewed), and then punch one of many stations per activity based on the count they achieved?
Say activity 1 has SI-stations with codes 11 to 19, labelled 10 to 90, and the students are told "if you manage 37 situps, you round that up to 40 and punch 40".
Activity 2 has SI-stations 20 to 29, labelled 0 to 9, and the students are told "you have ten throws of the basket ball, if you get the ball in the net 5 times, you punch 5".
When you download that chip, you'll have codes 14 and 25 and can thus work out whatever overall scoring you want to give.
Yes, it still feels to me like solving problems better solved with pen and paper, but actually a scoring system like this did exist in a product concept I bet you've never heard about but that will instantly look familiar to you on pictures:http://home.golfident.com/spelaren/