Either of those should allow you to achieve what you want to achieve. Find3’s goal is to work out which room or area a person/object is in via triangulation with the combination of signal strength bluetooth and wifi MACs. I think ReelyActive is more focused on generic presence i.e. which bluetooth MACs can I detect in my area.
Either way you’d need to run their nodes (your Raspberry Pi Zeros) and servers (maybe your OH box) but as there is no native binding for these you would probably have to write a script to query their API.