My idea was to have an in-game day clock (with days and nights). You can camp once every 24 hours (24 hours in Baldur's Gate isn't necessarily 24 real-world hours), and you can rest X-number of times in 24 hours. You can camp ANYWHERE, but if you choose to camp in a dangerous area, there is a chance encounter of being surprise attacked. In this case, you wouldn't receive all the benefits of camping.