Three ways

1.  We are a scrum shop.  Everyday we have 15-minute scrum and each team member tells what he/she did; what's next; any roadblocks.
2.  In addition to scrum, I check all the ticket status in our ticket tracking system at least daily.
3.  Cross-checking.  Check with other employees and pull feedbacks.

Honestly, I get anxious if I don't see projects progressing as I expect, especially with remote employees.  As a manager, I'm under the gun to deliver them on time.  As a remote employee, it's very important to keep your manager updated on ticket/project status, especially the high profile ones.  If there's any roadblock, make sure you bring it up early and ask for help (if needed).  A golden rule is "no surprise".