One nice use case of COBS is to clearly delimit packets being sent over a serial stream. Framing packets with zero bytes is particularly convenient for small projects because it’s easy to implement and debug.

I’ve used COBS and MessagePack combined for some embedded sensor projects. My implementation for Arduino (also includes some other functionality on top to encode data with MessagePack): https://github.com/telemetryjet/telemetryjet-arduino-sdk