If the command terminated successfully, then the backup is correct, barring a hardware fault (which could equally affect any verification you might perform). It may later become incorrect if the hardware is faulty, but most storage hardware detects corruption.
Nonetheless, if you wish to check the backup, the best way is to take a cryptographic checksum on each side and compare them. For example:
ssh myuser@myhost "sha1sum image.img" &
sudo sha1sum /dev/hda
Check that the two checksums are identical.
Note that this tests whether the backup and the original are identical at the time of the check. Anything you change on
/dev/hda, including mounting and unmounting a filesystem even without making any change (which will update a last mount date on many filesystems), will change the checksum. If you want to verify the integrity later, note down the checksum of the disk at the time of the backup somewhere.