Not hearing any sounds?

Try launching the app again, this time leave it on till the network activity spinner is completely done. Once it has successfully registered the device with the server, the app will never need to be launched again. If you continue having trouble get in touch, and I'd be glad to double check that it's been registered.

Why aren't there any options, settings, or configurations?

The main point of this app is to allow a smidgen of the unknown back into your life. With all the control oriented infrastructure we surround ourselves with, we are losing a very valuable human characteristic, the ability to deal with unexpected scenarios. Also, if you really want, you can silence your phone to avoid interruptions in really critical situations.
Another reason for the lack of configuration is that the synchronicity engine would be significantly reduced in efficacy.

The sounds aren't coming to multiple devices at the same time.

This is a little bit of a disappointing reality in the way push notifications are prioritized and sent to devices from Apple's central servers. Through our push provider (urbanairship.com), we do a killer job getting the notification requests sent out all in one batch, but the actual delivery to the devices can be mired in so many network issues that good synchronization just isn't reliable. We still feel that the 1-5 second latency between some notifications to multiple devices is still a very unique and powerful apparatus for meeting other Bzzt fans.

Like to contribute sounds and/or curate my own entire sound set?

Contributions are very high on my list of next steps, and I'd be happy to chat about doing custom audio sets as one off apps, sure.