DSynchronize is a stand-alone utility that let you periodically synchronize two or more folders on Hard Disk, Floppy Disk, LAN, USB Key, CD-DVD (with packet writing software) and FTP server. It's not exactly what the question is about, but the nearest thing I could find.
I, too was looking for a solution to the 1-minute minimum time in Robocopy and found this two-year old question. I ended up having this software suggested to me, and that's what I'm using. For the record, I have no affiliation with the software.
- Has real-time sync.
- Can add multiple folder pairs, and choose which pairs are active at a given time using checkboxes next to them.
- No installer, standalone program.
- You can exclude or include files through patterns or by modified time by clicking the 'filter' button.
- (others; see screenshot below. The checkboxes and buttons have additional help tooltips.)
- Is a GUI utility, no command-line switches available
- Folder pairs all share the same settings
The realtime sync option is marked in the screenshot under the section 'Special Options'. This would be what the question seems to describe as the goal. If it is not checked and you don't have a timer set, then you can to click the 'Synchronize' button to start a one-time sync.
How to sync two folders:
- Select a source folder which you want to monitor by using the browse dialogue in the top-left corner.
- Select a destination folder where you want to copy the changes to in the top-right corner.
- (Optional) If you manually typed-in the folder path instead of using the browse dialogue, click the 'TEST' button between the two boxes at the top to see if those folders actually exist. You will also want to check the 'Create folder if not exists' in most cases to make sure new folders are copied across, as it's unchecked by default and so the program only copies files by default.
- Tick the 'Realtime sync' checkbox. The syncing is now active, and all changes from the left side folder will be copied across to the right side folder.
I also found this YouTube video, which shows the software in action. It shows an older version and the options are not in the same place, but it provides a feel for how the software works.