With a 3 second google, I found your answer. Yes, you can use two fitbits with one computer and one dongle. Each Fitbit has it's unique ID number. You must have two different emails with individual fitbit accounts.Here is the link. https://help.fitbit.com/customer/portal/articles/1 76073-can-multiple-fitbit-trackers-be-used-in-the.07-02-2014 05:13 PM. With a 3 second google, I found your answer. Yes, you can use two fitbits with one computer and one dongle. Each Fitbit has it's unique ID number. You must have two different emails with individual fitbit accounts. Here is the link.