Don’t do it. I bought an older gigastone wireless backup device. It’s the square model. Worked great when it came out (iPhone 4s) but as years go by the developer was sold and the new app or older one will not recognize the device.
Rule of thumb is if the device needs a specific app to use they will stop updating it and the device will just end up in a pile of dead electronics.
I’m sure this is why it’s being offloaded here. It was $14.99 awhile ago and I wanted to get it but can’t do it.