Data Lifeguard Diagnostic is described as 'This is a Windows version of the Data LifeGuard Diagnostics. It will test WD internal and external drives. In additional, it can provide you with the model and serial of WD drives attached to the system' and is an app in the System & Hardware category. There are more than 25 alternatives to Data Lifeguard Diagnostic for a variety of platforms, including Mac, Windows, Linux, BSD and PortableApps.com. The best alternative is CrystalDiskInfo, which is both free and Open Source. Other great apps like Data Lifeguard Diagnostic are GSmartControl (Free, Open Source), HD Tune (Freemium), Victoria (Free) and iStat Menus (Paid).
CrystalDiskInfo is a HDD/SSD utility software which supports S.M.A.R.T. It shows the health status much more clearly than similar tools. The "Function / Graph" is especially interesting for the "Reallocated Sectors Count".
Victoria is a small application designed to assess performance, test and perform minor repairs to your IDE drive and SATA HDD. It's designed primarily for HDD repairmen in stationary conditions and is not intended to test the system hard drive.
iStat is a series of system monitor apps. It's available in different versions: iStat Menus, iStat for iOS and iStat Server as a companion application to the iStat for iOS app that lets you remotely monitor your computers (free for Windows and Mac).
Disk Drill is a data recovery software that easily protects your files from accidental deletion with Recovery Vault and recovers lost data from disks. Disk Drill supports most of storage drives, file types and file systems.
The smartmontools package contains two utility programs (smartctl and smartd) to control and monitor storage systems using the Self-Monitoring, Analysis and Reporting Technology System (SMART) built into most modern ATA and SCSI harddisks.
HDDScan is a freeware utility for storage devices diagnostics (HDD, RAID, Flash). The program can scan storage device for bad blocks, show S.M.A.R.T. attributes and change some HDD parameters such as AAM, APM, etc.