As researchers actually start to deploy Wireless Sensor Networks (WSNs) in 
the real-world, they are confronted with misbehaviors and problems not 
detected or seen during previous simulations or lab tests. Monitoring and 
debugging a deployed sensor network is often more difficult and more expensive 
than earlier in-house tests as the network might be hard to reach or located 
in an humanunfriendly environment. Furthermore, as these networks are 
optimized to fulfill their task with minimal energy consumption, it is hard to 
collect enough information to understand and solve such problems. The 
gathering of exhaustive information for debugging purposes would require 
changes to the distributed application thus modifying its behavior and might 
lead to additional bugs. In this extended abstract, we present our preliminary 
work on non-intrusive debugging of WSNs, which, as we envision, will shorten 
and simplify the deployment phase of future WSN applications.