The differences between the wireless systems and the BL2 data logger with or without Tracker MC/RH is the way they save and give access to review the saved data.
Wireless system with on-site PC: Measurements are saved by an on-site PC, and can be reviewed or downloaded for further data processing (e.g. kiln control systems). Remote log-in is possible.
Data logger BL2 and MC Tracker: The BL2 can save RH measurements or measurements from the Tracker in preset time intervals. To review the data, the BL2 has to be connected to a PC.