This was Hannah's birthday present when she turned 2 (Nov, 2000).   Built from a $37 bike from Wal-Mart.   It was never been ridden.  I tried to ride it by hanging on to the seat (it's so short that it's REALLY hard to sit on),  but I only managed to ride about four inches.  Eventually I scavenged the hub for another project, so it is no more.

Features:

• 12.5x2.25 tire
• 16 spoke steel rim  (spokes from the bike were used)
• 2.6 inch cranks (cut and re-welded  from 4-inchers)
• Suzue 36 hole hub
• Semcycle bearing holders

• Make a narrower hub for it (possibly by welding some flanges onto a bicycle bottom bracket.) 
• Put a child-size unicycle seat on it
• Smaller pedals that are barefoot friendly 
• Adjustable seat (after she grows a bit)
• How much it gets used.