Take a moment to realize there are "only" about 1000 weeks in 20 years.
Now think about your weekly patterns and start counting down.
Bonus depression for the morning, your chance of cancer doubles every decade.
This sounds like the perfect way to induce anxiety and hopelessness, ultimately resulting in depression.
This is a terrible idea.
I doubt that this kind of think will have a motivating a effect. Reminding you of the estimated point in time when your body degraded so much that you will die does not sound great.
It's also purely egoistic. How about making some else's life better by doing things you don't like?
You can either be a freeloader, roll the dice and see where the work of other people on medtech takes you, or you can help to increase the amount of time you have left. Participate in initiatives like http://healthextension.co/, or donate to the SENS Research Foundation.
It is interesting to see that in a community ostensibly focused on creating change the first response to length of life line items is usually that length of life and trajectory of life is fixed and immutable.
When I want to feel depressed, er, motivated I just figure out how many weekends I have left until I'm 78.
From all the complaining I hear from people past a certain age there's quality of life issues well before that magic number though.
Perhaps the backers are looking at it in a different way: time left to treasure.
I agree with other comments this is a terrible idea.