Review for Sync On Arrival by kudos2008
Rated 5 out of 5 stars
For those that are desperately seeking to override the version compatibility limitation, try installing MR Tech Toolkit (extension) first. It will then allow you to install this extension on an unsupported version. Works on 2.x. Have not tried it on 3.x.
To create your own collections, you must have a Mozilla Add-ons account.