"Staying fit together" should be something ALL partners involved are participating freely in and not forced on by someone else. I'm highly skeptical that thus a foundation would be motivational for the "forced" partner at all. Your presentation focuses more on the spying/pressing aspect than the benefits and how they would be achieved.

But even ignoring the "spy on your significant other"/"force your significant other to do something he/she doesn't commit freely to" part and concentrating on the "stay fit together" idea, I don't see any true differentiators/benefits for the $5 investment: There are already many solutions that allow to share and compare my fitness tracking data with others, often for free. In addition, there are many options to "stay in shape", like going to the gym, power yoga, pilates, running, cycling, swimming and so on. Your preferred method doesn't need to be the one your significant other might be interested in. Any solution to that?

To sum up: From the presentation I really don't see what the true unique benefit is that your solution provides to the users.