Apple intro'd built-in SD card slots with the last round of unibody Macbook Pros. The secret sauce is that the SD card is bootable -- you can install OS/X onto an 8Gb card, add some stuff like Techtool Pro, and use it as an emergency boot device.
Use case: your laptop's hard drive fails so you yank it, shove in a new one, boot off the SD card, and use your Time Machine backup -- you've got one, right? You're one of the Saved, right? -- to restore onto the new drive. Total elapsed downtime from hard disk crash to up-and-running again: 1-2 hours plus however long it takes to source a replacement drive.
(The fact that you can get photos off your digital camera is an accidental bonus. Because, hey, your camera is an iPhone in Apple-land ...)
Use case: your laptop's hard drive fails so you yank it, shove in a new one, boot off the SD card, and use your Time Machine backup -- you've got one, right? You're one of the Saved, right? -- to restore onto the new drive. Total elapsed downtime from hard disk crash to up-and-running again: 1-2 hours plus however long it takes to source a replacement drive.
(The fact that you can get photos off your digital camera is an accidental bonus. Because, hey, your camera is an iPhone in Apple-land ...)