If you just want a simple dashboard type of UI, you could look into using dashing (http://dashing.io/), which gives you a ready framework to start from. A user over at the SmartThings forum put together a nice dashboard running on a Nexus 7 tablet - [NEEDS UPDATING] Home Automation Dashboard (HAD) - Projects & Stories - SmartThings Community.
Starting with his Github code (GitHub - FlorianZ/hadashboard: Dashing dashboard for SmartThings. · GitHub) and just substituting for openHAB instead of SmartThings, I have a similar dashboard running off my openHAB server communicating via REST etc.
