SRT MiniServer
User guide

12.1.6. REMI: Tally

SRT Streamer PRO can receive Tally info from Studio and transfer it to cameras.
It supports:
1) NDI tally: if source is NDI cam then SRT Streamer PRO turns on tally lights on this cam
2) Web-tally: you can use smartphone as Tally. Just open  (change IP to IP of SRT Streamer PRO ).

Studio Side

On Studio Side you need SRT Mini Server (ver 2.4.5+) and any switcher with tally support. For example vMix.  Outputs from SRT Mini Server should be used in vMix by NDI.
So SRT Mini Server will receive tally info from vMix:
Tally info from vMix

Venue Side

You need SRT Streamer PRO. 
Go to Streaming setup and turn on "REMI Control" option
12.1.6. REMI: Tally
turn on REMI Control
After connection SRT Streamer PRO will be display Tally info received from Studio side:

Tally Lights

Current version of SRT Streamer PRO supports Tally Lights:
NDI cams with Tally (BirdDog, PTZOptics etc)