EastSign Mobile lets you electronically sign documents (and get documents signed) directly from your smartphone. Simply draw your signature on your touchscreen, and then the app will let you resize it to fit any document.
Cost: $14.99 for a lifetime subscription, or you can buy document credits at $1.99 for 5 docs, $3.99 for 10 docs or $5.99 for 20 docs.
Available on Android too? Yes