Just installed it. It's not a about pushing specific urls, but instead you push specific predefined data types. The ones available right now are "Note", "Address", "List", "File". Pushing is done by visiting the site at this time, though I can imaging a browser extension is in the works.

Personally, I don't think I'll use it - I use dropbox when I want to sync a file with my phone, Evernote for notes and lists, and just Chrome to Phone for addresses (via google maps) or urls.