How are penalties collected for weekly challenges?
Let's say you create a challenge with the following parameters:
Run 1 mile three times a week for two weeks with a $5 penalty.
A player in this challenge is required to submit video proof three times before the week ends, where a week is defined by when the challenge officially starts, which may or may not be the start of a traditional week. At the end of the week, a player that has not checked-in even once, will have collected three misses totalling $15 to the pot. This process starts over again on the next week.
It is up to the challenge creator and players to further define any of the rules and it's up to all players to regulate the challenge. For example, let's say a player has not checked-in once all week, and on the last day before challenge end, they submit 3 check-ins to satisfy the requirement. This is a pretty straightforward case of a user trying to cheat, as it is clearly against the spirit of the challenge. It is up to the challenge creator to flag two of these check-ins for being invalid.
Each challenge is different, and sometimes require special rules. It's up to the challenge creator to make these rules clear so there are no surprises.