gwabbit is an interesting product that was at WES this year. The app goes through your email looking for signatures. It then takes the information displayed in the signature, and uses it to add the person to your contacts.
The app was previously only available for desktop, but they now have a sneak peak beta available for download. The company is still putting the finishing touches on the app which will be made publicly available on May 26th.
[ED Note: The Beta link has been disabled but we'll let you know when the app goes live.]