standalone means.. it has a display . if it doesnt display A/F its a controller and requires a gauge or connection to a logger to see the A/F ratio
the plx SM-AFR module is not a standalone and would need to be connected to a gauge or logger or if running a wideband control chip with powerlogger it would run the anolog 0-5v output to the powerlogger wideband input on the powerlogger aux block
the plx m300 has a display but it still has output that could be run to a data logger or a wideband controlled chip setup with powerlogger