Let's start with developing our plugin. Create a directory for the plugin somewhere in your disk. As our plugin will select features within a given radius, we call it
Radius and use
selectradius as the name of the plugin directory.
Now, open you favorite text editor and create a file with this content:
[general] name=Select by Radius description=Select features in the given radius around another one about=Selects features of the specified vector layer which are located within the given radius around reference pre-selected features of the any other layer category=Vector version=0.1.0 qgisMinimumVersion=2.8 author=enter_your_name_here email=your@email icon=icons/selectradius.svg tags=vector,select,selection ...