Gravity Forms already makes it easy to build custom forms for your website. Have you ever needed your visitors to sign your forms? The Gravity Forms Electronic Signature Plugin can help. It allows your visitors to sign agreements with their mouse or on their touchscreen display.
The Gravity Forms Signature Add-on lets you control the size of the signature field and its color/background. You can set the field to be required or simply hide/display it conditionally. rednumber is the coder behind this plugin.