Data Collaborative integrated an e-signature into my app. It was a great experience and their product is top notch. I would recommend their products over others simply because they have a one time purchase model and their product works flawlessly.
DC Signature
Product Description: 
Add this simple feature to your Quick Base forms and save the signature as an image file attached to your records. It's perfect for situations where you need to validate that work was completed by an employee, approved by a client, received by a vendor, etc.
$299 per form
Installation:Our standard rate of $165 per hour applies if circumstances prevent a normal installation, or if assistance is needed in setting up Quick Base and client meetings are required.
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