When looking at the SM website it can be confusing trying to work out what you need for a logger.
The following list is an attempt to identify the basic requirements, plus a few extras you might be interested in.


Minimum for F5B logger / limiter function:
     UniLog2                                                                      part no.    3000
     400A current  sensor:-
          - for battery with female on +ve terminal       part no.    2517   (white writing)
          - for battery with female on -ve terminal        part no.    2537   (black writing)


Common extras:
     brushless rpm sensor                                              part no.   2213
     temperature sensor  (best / smallest)                   part no.   2225
     temperature sensor  (cheaper)                              part no.   2221
     


Other optional items:
     patch cable for telemetry to Rx                               part no.   9101      (if you have a telemetry radio)
     pitot tube speed sensor                                           part no.   2560
     UniDisplay                                                                   part no.   2400