This is what the Status widget is for. It is a good idea to create a Status widget on your dashboard for each device referenced there. This will give a live, visible indication of how the device is working. Remember to set a sensible heartbeat, several times greater than the device's update rate (if there are no updates in this heartbeat time, the timeout status is triggered).
This is what the Status means:
It may also be a good idea to set up a warning Event to let you know if any particular warning/error comes to pass. The greater the number, the more concerning the error so setting the trigger as above 60 would let you know if the module reports an error (eg low batt) or loses communications with a module as well as if there have been no comms at all with the device since the heartbeat period elapsed.
Another useful tool is a table with historic Status data in, similar to this:
Column 1 is a date type column, column 2 is a value type column based on the status variable, column 3 is a context type column based on the status variable with the following further settings:
