The VE.Bus Smart dongle is two products in one:

First, it is the Bluetooth accessory for our range of inverter/chargers:  Multis, MultiPlusses, MultiPlus-II, MultiGrid, MultiGrid-II, Quattros, and our series of Phoenix Inverters with a VE.Bus port.  When installed, use the VictronConnect App to monitor operation and also operate the system:  Change the input current limit as well as switch between Off, On and Charger-only modes.

Second, it can work as a voltage and temperature-sense device for the inverter/charger.  This works with all models.

For monitoring, the device is a great alternative in caravans, smaller yachts and motor homes when a Color Control GX or Venus GX is a step too far.