He has contributed to various open source projects including GWT-Maven, Android-Maven, Gwitter, and is coauthor of Manning's GWT in Practice and Unlocking Android. Michael Galpin is the architect for mobile software development at eBay. Matthias Kaeppler is in charge of mobile development for the online review company Qype, and he created or maintains the Android open source projects Signpost, Droid-Fu, and Calculon.