We examine multi-player pervasive games that rely on the use of ad-hoc mobile sensor networks. The unique feature in such games is that players interact with each other and their surrounding environment by using movement and presence as a means of performing game-related actions, utilizing sen- sor devices. We brie y discuss the fundamental issues and challenges related to these type of games and the scenar- ios associated with them. We have also developed a frame- work, called Fun in Numbers (FinN) that handles a number of these issues, such as such as neighbors discovery, local- ization, synchronization and delay-tolerant communication. FinN is developed using Java and is based on a multilayer ar- chitecture, which provides developers with a set of templates and services for building and operating new games.