The webadmin page displays the current game status in the top right of the screen which includes:
- Map
- Current player count
- Max player amount
- Current wave
- Maximum waves
This is returned in HTML format so needs to be parsed if you intend on doing something smart with the output. However getting it is a little tricky due to it being behind the webadmin's login wall.
curl http://server:8080/ServerAdmin/current+gamesummary -b authcred="<authcred>" -b sessionid="<sessionid>" -X POST