Use your old smartphones to create a wireless or wired in-ear monitoring (IEM) solution for your rehearsal room for almost free. If you already have a digital mixer that can be connected to a laptop (PC/Mac) you're good to go. Obviously you wouldn't do this live on stage for performance, but for a small budget you can get a quite room with almost no additional equipment.
I have made mixed experience with iPhone and expecially iPads using wireless. Having an Ethernet cable attached usually gives a stable connection, less crackles and lowest latencies.
iPad Air 2 (2014) and iPad Pro (2017) did not work over wireless at all.
Funny enough the iPhone 6 (A1586) which also came out in September 2014 worked great over wireless like shown in the video. This may be due to the fact, that it's using old WiFi 4 frequencies that might not be at used at all in my home as every other device fights for WiFi5 frequencies.
Actually none of my newer iPhones (Xr, 12, 15) worked flawlessly over WiFi5.
However if I installed a WiFi 6 router, things were better. I used a cheap Behringer USB interface on the iPhone15 and got decent ping times of about 3ms and an overall latency of 10-13ms. I could play the drums and here myself over in-ear with some effects like Reverb and Compression. A simple USB-C to Audio converter for iPhone should do the trick as well - maybe I get one of these...
I do however recommend to set a MANUAL jitter buffer, once you've sorted out your setup (I had 7 or 8 ms).
Let me know which devices worked for you over a wireless connection!
I don't have any Android devices to test. Would be interesting as well :-)
Needless to say, that your PCMac running as the "sender" Sonobus app MUST HAVE A WIRED CONNECTION to your Router! Don't lose precious milliseconds of latency with a wireless connection here.