When you care enough to send the very best and most geeky greeting card you can find, you'll probably settle on these cards from Urban Outfitters' Web site that we spotted on always-on-top-of-cool-tech-stuff blog Geek Sugar. Just like the digital message tape we covered once, these cards are customizable for a whole range of geek-specific occasions...
These recycled paper "LCD Cards" come embossed with two rows of eight little digi-text canvases. To write "HAPPY BIRTHDAY," "MISS YOU" or "WE GETN MARRIED" (You know these would make awesomely techie engagement annoucements!), you just ink the corresponding spots on the card to "digitally" display your message.
The 7.5" by 4" cards come from the good ol' USA via the Yellow Owl Workshop, a stationery company and studio run by artist Christine Schmidt in San Francisco.
Order them from Urban Outfitters here. The Web site says the price is $5, but there's no mention of how many cards you might get for that price. If it's only one card, this might be one idea that's better put in the inspiration folder rather than the shopping list.
Maybe you could design your own thin-lined template of blank LCD shapes and get it printed onto blank cards for a cheaper ink-in-in-with-a-thick-Sharpie version.