I use the Icotec GC500, great caller but the claimed range of 300m is total guff.
The advantage of a remote caller is that I live some distance away from where I shoot so baiting isn’t an option, furthermore, baiting is severely limited by the wind direction at the time, the fox won’t smell it if the wind isn’t carrying the scent in its direction.
When I arrive at my chosen spot, a quick assessment of wind direction and I can set the caller 60 or so yards away in a position that the fox won’t cross my scent trail to find where the noise is coming from.
All that said, I do believe that the effectiveness of such callers may have been over exaggerated except maybe during the mating season, that is certainly when mine has been most effective and also coincides with me not being able to impersonate a fox looking for a shag.
The callers come with a ridiculous number of calls, first thing to do is to whittle that right down so that you aren’t spending more time fannying about with the remote than you are scanning the field.