Needs more features
Beyond that, there isn't much else. You can set the app to notify you via pop-up, but then there's nowhere to change it. I originally set up the app, presumably, at around 2 p.m., because that's when the notification pops up. I'd really like to change the time of the notification, since two o'clock is not very helpful. Also, even agree you check off that you've done today's challenge, the notification still pops up. It also pops up on rest days.
Another desirable feature would be to allow the user to enter additional swings over the allotted amount.
One complaint: the app is set for DOUBLE SWINGS. Most people don't do double swings (i don't personally, because I'm short and cannot manage two bells on the back swing without drastically changing my form). The app is called "Kettlebell Swing Challenge," not "Kettlebell Double Swing Challenge."
I only downloaded the free version, to try it out, but the lack of features and no way to contact the developer (the contact link takes you to his private Facebook profile...?!) make me unmotivated to purchase it.