Great to hear that you are interested in a master's thesis topic with our group. We always have several topics at available. It is probably best to swing by and talk to us in person, e.g., by emailing us or coming to see us in second floor of the new main building. Looking forward to talking to you!
PS.: if you have taken any HCI class in the past, you probably have a wiki account already, so feel free to get a preview of our available projects.