Ok, as long as you brought it up...
There is no denying that the pieces for Binary Homeworlds (and four player Martian Chess and a bunch of other games) map onto Mü cards. BUT each piece is still something like 2.5" x 3.5". Easy to transport but a little space intensive to use.
I'm quite the fan of Zarf's Zarcana pieces:
http://www.eblong.com/zarf/arcana-pieces.html
I made mine out of 1/8" plywood. I don't know that I followed Zarf's size standard (.5", .75", 1"), but by happy accident four of my larges, four mediums, and four smalls can be fit on single poker sized playing card with just a little room to spare. This has two implications:
1. I can use those clear plastic card boxes to carry these around. Enough for B.Homeworlds would fit in a 3/8" box.
2. We (either Looney Labs or some group of rabid rabbits) could make cards with a S, a M and a L of four different colors using the same material and process as Pirates of the Caribbean. For B.Homeworlds, you'd need three such cards. Five of these cards would be sufficient for RAMbots, Zarcana/Gnostica, Zagami, four player Pikemen, six player Martian Chess, four player Homeworlds, two simultaneous games of Martian Backgammon, or even three player Treehouse.
Using either a larger card, or cutting out smaller squares might allow us to get one of each size of FIVE colors on one card. Someone will have to try some experiments to see whether such pieces would come out too small.
Sure, on the page linked above, Zarf mentions a paper implementation of these pieces, which were difficult to handle. I think the Pirates plastic would give them sufficient bulk to make them usable.
Ryan
P.S. If we wanted to push that medium a little further, we could make it so that each pyramid is constructed out of two plastic triangle that slip together. THAT would be cool. Of course, it would be hard to stack such pieces.