Riot and Matrix. For daily communications among collaborators, we've been using Riot.im, which is a slick client (on smartphones, in browsers, and with desktop clients) for the Matrix protocol. Matrix is intended to be a decentralized chat and VOIP protocol -- decentralized in the sense that Matrix server software is open source, can be run independently (even on a single-board computer like a Raspberry Pi), and can be federated. It is also intended to be a 'bridging' protocol: multiple other messaging protocols are currently supported (e.g. Slack, IRC) and interfaced by a Matrix server. Conversations and threads are organized within 'rooms'; VOIP seems to be stable, even in relatively low-bandwidth networking conditions (comparing favorably with Skype and Google Hangouts); and there is the ability to manage 'integrations' such as attatching an Etherpad (collaborative document editing) to a 'room'.
Electric fence monitoring.