We set goals and update each-other on them weekly.
Everyone owns their schedules, their 'rocks', their deadlines and their own time. If projects are consistently lagging behind, then we re-evaluate the system and management, but we don't find the need to monitor productivity as such in a remote team.
Productivity is measured by team leaders on each team, and it depends on the nature of the team. For example, support teams are measured by the number of tickets answered customer’s rating, pace, etc.
We just check if the work is done, in a reasonable time.
No measurement at current small team (5 people.) It's pretty obvious when someone is struggling and we need to help or change the situation.