I don't know of any and I doubt they exist. The problem is extremely challenging since open files may not be consistent. Even if you're using Linux where the concept of a deny-read lock doesn't really exist, or on Windows with Shadow Copy, the only way to guarantee that the disk is in a consistent state is to not only fully quiesce I/O to the disks but flush all caches (app and OS) to disk before doing so, and make sure that all open applications put their files in a state where they can recover cleanly from a sudden power-loss and keep them there for however long it takes to take the disk image.
I'm not saying that it can't be done, I'm saying that it is exceedingly tricky to make something that'll do it and work as reliably as the offline imaging methods we've been using for over a decade.
The more fancy virtualization solutions do something kind of like a live disk image, but they're also snapshotting the running memory when they do it. They can get away with this since they can be sure to load the snapshot-memory before starting off of the disk snapshot, real hardware doesn't have this luxury.