I love this app and use it frequently and this prediction is part fun part speculation. So here it goes:

Check out their website : https://actifit.io/
Google play link :
https://play.google.com/store/apps/details?id=io.actifit.fitnesstracker.actifitfitnesstracker

Give the app a 5 star to help the fellow STEEM devs.

Now on to prediction :
I delegated 100 SP few weeks back and got my first payout ( 400 AFIT for 1 week) which turns out to be ~ 1600 tokens per month. From a pure investor perspective if I had invested the same 100 SP with @smartsteem , I would have made the following daily:

Which turns out to be 1.55 Steem monthly.

So , in rough comparison , 1600 AFIT tokens equate to 1.55 STEEM or 2.23 USD ( per today's prices)
Or 1 AFIT token = 0.001395

But of course , we are going to moon with STEEM , so let's re-run the number with STEEM hovering around 100 USD ( butterflies??)
1600 AFIT ~ 1.55 STEEM ~ 155 USD
or 1 AFIT token = 0.096875

Now keep in mind you can easily earn 35 token by just walking 6000+ steps so that comes out to be
35X31X0.09 = 104 USD
You could be making this amount of money by just walking on regular with this app.

Walk on

Edit :
@mcfarhat informed me that since I started mid-week the weekly AFIT token payout was 400 instead of 700( weekly) , so here are revised numbers
2800 AFIT monthly ~1.55 STEEM
at current price ( 1.44 USD for STEEM) 1 AFIT = 2.23 / 2800 = ( 7.971428571428571e-4 )

at 100 USD ~ STEEM price = 155/2800 = 0.055 USD

Monthly potential for 6000 steps( taken daily) , at 100 USD STEEM = 59.67 USD
Still not too bad !!