SSH (and SFTP) server on Android discoverable through avahi/bonjour
I have been using the free SSHelper (without rooting) since it recently added zeroConf broadcasting. It provides an SSH and RSYNC (file transfer) server, while also broadcasting a ZeroConf name. Another avahi/bonjour client can connect without needing to know the android hostname. Explained in more detail in this other answer: Set hostname for SSHelper