I recently had my computer company tech chap looking through my computer via remote (I'd had some unexplained freeze-ups and a crash), and at one point, I saw him use the Hard Disk Sentinel.
Not sure it would be of advantage for me personally to install it though because I don't know enough about what to do if a problem is found.
It showed the status/condition of each disk, and on the two larger disks it also showed temp. It didn't show temp on the SSD.
All three had 100% pass with this result: The hard disk status is perfect. Problematic or weak sectors were not found and there are no spin up or data transfer errors.
It appears to check internal and external disks as I see the hdsentinel.com site describes it as:
No need to use separate tools to verify internal hard disks, external hard disks, SSDs, disks in RAID arrays as these are all included in a single software.
They also seem to have a special offer at the moment for €12.50 to download.