I love this desk. It's Steelcases's "Sit-to-Walkstation"
I've thought about building my own treadmill desk but my concern has been that certainly at times I'll need to sit.
This desk can do both (it moves).
It can be yours for "just" $4,899
(BTW, in case anyone's feeling stupidly and irresponsibly generous my birthday's at the end of August)