10to8 has a widget for booking your service on a calendar, if someone can create an app that embeds the widget please share the steps. More details about the widget can be found in above link.
Add it with the web viewer ? 
If it is a HTML5 (with embedded Javascript) widget, Then you can simply open the link from webviewer box that you create within the app. Personally I use a lot of widgets… but not too sure about 10to8 though