One of the problems that I perceive with Recoil is getting each phone paired to the correct blaster. If you have a big group and try to pair multiple phones at a time, different phones may pair with each blaster. I use a QR code taped to the blaster to help ensure that the right phone is paired to the blaster. The QR code just contains the MAC address for the blaster.
I generated the QR code at https://www.the-qrcode-generator.com/ and saved it to SVG. I opened it in GIMP using 100 pixels per inch and specified a 1 inch sized image. I printed the result, cut it out, and used some clear packing tape to get the QR code onto the side of the blaster.
On a side note, I know there are bugs, and there are things that I'd love to be able to improve in this app, but I just don't have the time right now to commit to it. Maybe someday. This is just a small update that took me all of 20 minutes to do. I did it because I thought it was a cool idea and it was simple to implement.