I don't think this really is what people might call a sandbox but it can optionally block or allow syscalls happening (in my mind only one aspect of a sandbox) and it looks like it's interactive. I think this is great. OpenBSD has had great success with pledge and I have been experimenting with seccomp (via the libseccomp project) with both Node.js bindings and a cli in C for doing a very similar thing as Sandy (although not interactively, which is a nice touch).