I have a wrist Contec CMC50F too, my how times have changed. Mine cost A$42 a few years ago, still works well. Unfortunately now with the way the medical prices have skyrocketed due to demand because of Covid 19 the prices are now up around A(Australia)$250
I've been using Sleephead for years and now its Oscar, same thing but probably updated. I also use my Oximeter from time to time. Yes Oscar does allow to download from certain Oximeters. HOWEVER, if your a mac user and running a later OS than High Sierra you may have problems getting a driver so it can recognise the Oximeter. Its a bit complicated for Mac users as you still need a driver for the earlier OS as well. The makers of most Oximeters, Contec, do not supply reading software for Macs. I read it in my Oscar software but as I said for mac users its not straightforward.
I can sync the timing of the Oximeter to the CPAP time so I can do direct comparisons to what the CPAP machine has recorded at the same time. By the way my second iMac runs Snow Leopard, for that OS you'll need the old Sleepyhead software as Oscar doesn't run on Snow Leopard.
As an exercise I compared my wife on the CPAP machine for one night with a CPAP mask and machine working normally with a night with no CPAP machine just the Oximeter. This was done to see if there was any improvement in oxygen intake with the CPAP system. It would be hard to believe there wouldn't be but by how much difference does using a CPAP machine make.
After doing the exercise I can report that there was only a 1% improvement using CPAP in this case. As there were no dips in oxygen levels this single exercise indicated that the CPAP machine and all the money didn't seem to make much difference in oxygen intake. Interesting I thought. My wife has been using a CPAP machine for over 15 years. I will do the exercise again sometime but I thought it was an interesting experiment