Can I give a remote simple input to multiple devices without wifi?

I'm using an app for a theater project. The idea is that there are a few phones in the audience and some audience members are receiving text messages from characters in the show.

A few details.

  1. This app will only be running on about a half dozen phones, we'll be hiding in the audience before seating.
  2. These phones won't be connected to a service plan.
  3. We'll be doing this in venues where we may not have access to wifi.
  4. The show itself uses prerecorded audio, so once the program starts, if it starts at the correct time, it will be synched enough to the show.
  5. This is a show built for a small audience arranged a particular way, so the devices should never be more than about ~20 feet away from the backstage area.

I've put together a program that I'm happy with which displays the messages with the correct timing. Right now a button press starts the sequence. The problem is that since we want the phones to be pre-set before the audience is there, there's a little bit of variability in whether the show is able to start perfectly on time, which would throw off the timers.

Ideally I would love some way to essentially push that button on a half dozen phones from backstage. I'm wondering if there's a Bluetooth approach that would work, or some third party app or extension which can somehow send that GO signal to all the phones.

Apologies if this is too broad. I've searched the archives and if there's anything that applies, I don't know enough about that approach to see it yet. I've seen references to a bluetooth shutter, but they don't seem to be able to pair with multiple devices.

Any suggestions are very appreciated.

You could try bluetooth and keep the app up and running during the show

You will have to use several bluetooth components on the sender device, for each connection another component...

As a start see

To keep the app up and running use the KeepScreenOn method from the tools extension App Inventor Extensions: Tools | Pura Vida Apps


Thank you for the link.

Someone on another forum suggested it might be possible to use a wifi hot spot or router and have the phones automatically connect and listen for that connection as a start signal. Is there a chance that App Inventor has a way to recognize that connection as a trigger? Or a third party plugin?

I feel like if that might be easier to implement than building a separate program that tracks each phone individually, if it's possible.