The VE.Bus Smart dongle is two products in one:
First of all it is the bluetooth accessory for Victron's range of inverter/chargers: Multis, MultiPlusses, MultiPlus-II, MultiGrid, MultiGrid-II, Quattros, and their 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.
Secondly it can work as a Voltage- and Temperature-sense device for the inverter/charger. This works with all models, but is especially useful in combination with the MultiPlus-II, as it does not have on-board terminals for Voltage- and Temperature sense wiring
For monitoring, the device is a great alternative in caravans, smaller yachts and motor homes for which the Color Control GX or Venus GX are a step too far.
For more information, please download the manual here. Note that the Multiplus or Quattro must be updated to the latest firmware in order to utilize the dongle. Features are being added, please see the manual for capabilities at this time.