Slack with access to video calls at need. I've worked remotely for over 8 years at 3 different companies. Two have had some variation of this (Hipchat/Slack +

Slack with access to video calls at need. I've worked remotely for over 8 years at 3 different companies. Two have had some variation of this (Hipchat/Slack + Google Hangout / GoToMeeting or Slack calls) and it works great. We have a daily standup meeting on video and then we can jump on a video call through out the day if we find a need for it. Otherwise, I have clear focus through out the day - I can choose whether to respond to slack notifications or turn them off and work through them later.