internal Communication for travellers

I am from India. Have faced this problem before 5 months while travelling from Chennai to Bengaluru on train. It's a 4hr journey. My phone didn't work. I was in a need to attend personal emergency call. Since my charger didn't work, couldn't answer my calls.

So my idea is to build an internal communication app for passengers who are travelling. It will be really helpful. Let's say, if someone is not well during travel, we can send out a message on group saying " Personal emergency, any doctors travelling?" and share on the app. The app should show only the passenger's seat no. Message limit can be upto 5 or 10.