Roeland submitted a radio button list widget in the appstore. It supports enums and booleans. Go get it!
Radio buttons are not available in 2.4. You should handle the 'one exclusive selection possibility' by using microflow. In the next 2.5 release you can use a custom widget in order to get radio button functionality.
There is a workaround available though; if you would like to have a radiobutton with for instance the options 'good' and 'bad' (which you would normally do with an enumeration), you add two attributes of type 'boolean' (one called 'IsGood' and one called 'IsBad').
In the form, you show both booleans as checkboxes and with the aid of 'on change' microflows you ensure that only 1 of these booleans can be checked at the same time