MacGizmoGuy shares his quarter-century of Apple computer experience to help folk find insanely great Macintosh gadgets: Mac SSD and HDD backup drives, OSX web cameras, Wireless Bluetooth and USB speakers, Microphones and Audio accessories, Keyboards, Mice, Printers - and more.
Apple's introduction of a Secure-Digital - SD card slot in 2009's Unibody MacBook Pro and Aluminum iMac has appeal for certain Macintosh owners. For many, the built-in card slot which supports both standard SD cards AND SDHC high-speed and high-capacity flash memory cards adds quite a bit of versatility - not just for digital camera use, file backups, PDA or MP3 storage - but opens the option as a bootable SD card for Mac that can come in VERY handy for road warriors who can't afford downtime on the road or want a wafer-thin startup disk for running disk diagnostics and other system utilities.
For emergency startup use, consider a 16GB SDHC card at a minumum to hold both OSX install (about 6-12GB) and extra room for critical 3rd party apps and a few utilities - with room to spare.
With a passive SD adapter - Apple's SD slot can accommodate smaller form-factor cards such as MMC and MicroSD cards as well - eliminating the need for an external USB card reader for many.