Oh and for those who haven’t noticed it just yet: the SimvarWatcher example application in the latest MSFS SDK (version 0.12) does support “string variables”: there is an additional “Is String” checkbox, which should allow to actually observe simulation variables such as the previously discussed ATC RUNWAY AIRPORT NAME variable.
Unfortunatelly this little new feature apparently brought other issues, one of which can be worked around quite easily (simply add “False” to the stored file entries), the other requires an actual “parser fix” in the C# code (seems like the parser “swallows” the variable index like :1, :2 etc when loading a *.simvars file):
(I have submitted this to ZenDesk already)