android phone to bridge - guest to studio

hello,

is there an application for direct streaming from a phone to BMD bridge

As far as I know the ATEM Streaming Bridge only works with streams generated by Blackmagic streaming devices (such as the ATEM Mini Pro, etc.). I haven't heard any reports yet of people getting the Streaming Bridge to work with 3rd party streaming encoders or streaming software. Apparently there are some differences in the stream metadata that are difficult for most of the popular open source RTMP streaming libraries to generate at the moment. There were some earlier discussions about that here:
viewtopic.php?f=4&t=146121
viewtopic.php?f=4&t=121096

Note that there are other RTMP streaming decoders out there that may have better compatibility with arbitrary RTMP streams from other sources. And it's also possible to create your own kind of streaming bridge with a Raspberry Pi (or other computer) running an open source RTMP-capable server software such as Nginx. See this thread for a discussion of some of those options:
viewtopic.php?f=4&t=115156

thanks Dave for this complete resume of situation.

for studio side, your link to pro convert or Roman's raspberry solution seems attractives. I'm not familiar with PI and may be some optimisations are required...

for GSM side, do you have advices on applications dedicated to rtmp/srt streaming I searched and did not found "broadcast use" APK.