There are many research efforts on situation awareness in smart home with a single user. However, a harder problem is situation awareness when multiple users are present. We investigate the problem of recognizing multiuser activities using wearable devices in a home environment. The objective is to provide situation awareness so that a smart home can respond to the needs of its residents based on their activities. An important part of the research is to detect whether there is any service conflict resulting from the ongoing activities. If so, a conflict resolution algorithm needs to be applied so that an acceptable service by multiple users can be achieved. To verify both the activity detection and the conflict resolution algorithms, two experimental systems are constructed with different architecture alternatives to evaluate the algorithms and decide the most efficient implementation design.