Look for supplied participation
A challenge can place individual walkers into a field or onto teams. That removes the awkward invitation stage and makes the activity available to someone whose friends use different phones, dislike competition, or live on incompatible schedules.
Check what the challenge counts
Some challenges count every step, including movement around the house. Others count deliberate walking sessions. Neither is automatically better; choose the one that matches the behavior you are trying to build.
Avoid challenges built around one enormous target
A distant virtual route can be entertaining, but it may not create weekly accountability. If consistency is the problem, prefer a format that resets often enough for a fresh start and gives each week a clear result.
Choose fair competition
The best challenge gives newer and experienced walkers a meaningful role. Matching teams or opponents by recent performance is more welcoming than placing every participant on one enormous raw-step leaderboard.