Some examples that I've seen:
1. Captive is mummified in saran wrapped with scissors wrapped to their back just out of reach.

2. Captive is subjected to two hours of sensory deprivation bondage. The captive is supposed to give a signal when the allotted time has passed. If the signal occurs before the goal time, 15 minutes is added. This takes advantage of the disorienting affects of prolonged bondage, making it difficult to know exactly how much time has passed. And of course there is a safe word.
3. Two captives, both hogtied. One is blindfolded, but can still speak. The other can see, but is gagged. Together they must coordinate an escape.
These are the sort of things I'm talking about. I guess it's difficult to put a label on, but its really anything that makes the bondage into a game. Not a simple "escape in the allotted time" game, but a challenge nonetheless. Anyone have any ideas?