The main contribution of bot-bottle is the idea of a "bottle". It's an easily defined, composable definition for how an agent can interact with the outside world, and doesn't depend on anything harness or model specific.
Bottles help solve the "exploit through trusted channel" problem by reducing the size of that trusted channel to be as small as possible, keeping credentials away from agents, and monitoring everything that comes in and out so leaks can be detected (either in real time when easy, or later via forensics if a more complex exploit gets by so you know what happened)
Mobile support was also pretty important for me and how I use coding agents, so I provided a way to interact with and unblock agents on my phone regardless of the harness or model.
Let me know what you think! Feedback on the threat model and the bottle abstraction are especially welcome.