What are some alternatives?
When comparing Zeplin and Pamela for Skype, you can also consider the following products
Invision - Prototyping and collaboration for design teams
Mightytext - Send & Receive SMS Text Messages from your computer. Sync'd with your Android #
Framer - Bring your designs to life.
ActiveWords - Other Collaboration
Balsamiq - Balsamiq. Rapid, effective and fun wireframing software.
Abstract - A secure, version-controlled hub for your design files