I've used them in a few different applications, in my boats, motorhome and the Kawasaki Mule on the ranch. I use them in Bluetooth mode because I'm close enough to the devices when in use.
Also I found that when connected to WiFi it provided a backdoor into my home network. There's probably a method to secure them- I disconnected them from my whole house audio and didn't get around to researching that any further.
You need to use their app to group multiple devices together; it's a bit clunky but it does work
. There was no way to adjust latency when multiple devices are playing the same material and the echoing was bothersome. But that was in my home with the devices a fair distance from each other. I haven't tried them together in the boat where I am using 3 of them.
Tagged into my Alpine stereo system via Toslink it works nicely, the others via the 3.5mm/RCA adapter to 12vdc amps. The devices are powered with a 12v usb hub.
I access and control via my iPhone
and iPods. Usually play Sirius/XM app, podcasts, Youtube and stored music