Fault detection/failure possibility detection in Xbee+Arduino

Background: I am using Xbee+Arduino as nodes which are distributed (hypothetically) in wide area. Now I have a coordinator which controls number of nodes.

My question : Is there anyway to detect the performance of the nodes according to it's failure? What I am trying to say is I want to detect the nodes' possibility of being failed before implementing in field. Is there anyway to test this for Xbee+Arduino?

The concept I got so far is about how to detect the failure (after it occurs) using different algorithm, but I want to detect or determine the percentage of its failure in near future; or is there any simple way for this node (Xbee+Arduino) to send a message or signal if it is dying or disconnecting?

Thanks for the answer in advanced.