Yeah maybe. But I got it working anyway using 'child_process'. So typical to find the solution right after posting a question!
var f = File('D:/PhotoshopExporter.exe'); f.execute();
With app.system you can open anything!
Here a example:
app.system("cmd.exe /c\"C:/Program Files/Adobe/Adobe Illustrator CC 2014/Support Files/Contents/Windows/Illustrator.exe\" );
I get an "app is not defined" error when I tried your method, so I guess you need more code than just what you supplied in your example.
In any case this works fine and I don't see a reason to do it another way.
var exec = require('child_process').exec; exec('C:/Windows/notepad.exe');