Thanks to Franko, the developer of the official NetPanzer Android App, you can have today instant notifications of online players on your phone.
Just install Telegram (either on Android or iPhone) and join the channel 'NetPanzer Gamers'.
You can then choose what type of notifications you want (with sound or silent etc).
Telegram link to our channel: t.me/netpanzergamers
With the Android App you already had a full NetPanzer server browser on your phone.
By joining this Telegram Channel you will get notifications when players are online and playing.