The Bilge boxes can monitor both liquid in the bilges and and also any gas build up. Specifically, the gas sensor detects CO and other flammable gases. This means it is very sensitive to any batteries that are sulphating, and also any exhaust leaks from the engine(s).
As with other peripheral boxes you can have up to 6 boxes in the system. They can be connected using network cables or by RF if there is an RF distribution box connected in the system. If using RF then the box needs a local power source which can be either 10-36v DC from the boat batteries, or by a 5v supply on a micro USB connector.