What tools read SMART data and can run on USB bootable media?
The process to make your own test rig is quite easy:


Install OS X onto a USB hard drive. A partition with 20 GB should be just fine.
Use the Startup Disk preference pane to reboot to that new OS and create an admin user.
Install homebrew - https://brew.sh
Install smartmontools - brew install smartmontools 
Get a USB drive or SD card if you don't want to boot from the hard drive/partition.
Thin out files if your image won't fit on the chosen media (or buy larger media)
Use Disk Utility to Restore the OS from the partition to the media chosen


Now you have a UDB/SD card that can boot your Mac and run one of the best free SMART tools.