After we linked to instructions for how to burn a Lion boot disc earlier this week, Nature's Eye Studios contacted MacStories to let them know they figured out how to get the new OS to boot off a SD card. After downloading Lion from the developer site, the video maker proceeds to wipe a SD card and use the repair option with the Lion disk image as the source to create the boot. Once you've created the backup, you can use the SD card as a Lion installer if needed, then pull a backup from Time Capsule.
Keep in mind that the final release of Lion will include a restore partition and Recovery Mode, meaning that you'll be able to boot your machine from a clean Lion installer at any point without the use of external media (assuming your hard drive's not wonky). While this means you're a lot less likely to need install media down the road, it's nice to know the option is there.
Check out the video below to see this process in action.