I am using SK and Skyecho on my android device (8inch tablet) since 2 years, and I like it a lot.
My android device has also mobile data available, but unfortunately, SD <-> SkyEcho connection does not work 100%, ig mobile data is switched on.
How it is, on my devices (tablet and phone):
Mobile data off: SD and SkyEcho work great, as well traffic visualisation as configuration of skydemon from skyecho menu (thats important, as I switch often the plane, and so I dont haver to enter hex code each time - its done by skydemon!). Live weather / notam data are unfortunately NOT available, due to no internet connection.
Mobile data on: SD and Skyecho connction work basicly, means - traffic visualisation works (so the main functionality is given), but configuration is not availabe (If I click in navigation mode in SD to Sky Echo Configuration, SD cant find my Device). But - as said - traffic information are recevied - so a basic connection seems to be there. Also on browser, the IP of the device is not reachable. But of course, live weather is available,
I think, this is not a SD issue (but not sure), but maybe someone else has this issue and found a workaround?