UPDATE Looks like as I was writing this as @Sijaka beat me to it and gave you some great advice, No point deleting what I wrote, so it is still here if you want/ need it
It sounds like you have done just the right amount of research and know what you want, and they all sound realistic, feasible and do-able
The guys above have given you most of the answers, so I will try to fill in the gaps
S9 and S20 perfect
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you will be able to make your Business card while you wait
For you door access, since you are in the perfect position to buy yourself something compatible right from the start, This community is in the process of developing a door lock, but there is no deadline at the moment
Here is the link to that thread
This is a thread with some compatibility systems, although it may be a little out of date
Samsung used to make the Ezon door lock, but they changed to firmware and is no longer compatible…unless you can find an old one but in saying that, there is a new one released by them that will be available soon / now-ish
Very early in the video
00:00:23 - 00:00:32
There is some other options around, THIS being one of them, there is an implant that is compatible with it
The firearm bit you MAY be referring to is a system Amal made, here is the interview where he demonstrate it while still as prototype
Here are some good videos for you to watch for using the xAC
Wiring
Programming
Gym??? What Gym is it, if it is a mainstream / global gym, somebody on here may have the same gym card???
I think that is everything, and we have probably narrowed down your choices, when we get all the info, we can give you actual Implant recommendations, I would however at this point definitely put a NExT in your shopping cart…