Today I started to test the developer-version of the upcoming QGIS 2.14 and found a nice feature integrated out-of-the-box. In previous QGIS-versions tracing along existing geometries required 3rd-party plug-ins (e.g. http://isticktoit.net/?p=131) – now it looks like integrated with QGIS 🙂

Update 7.3.2016: Lutra Consulting describes all details in it’s Blog