Well, it took a bit longer than I anticipated, but finally the IntROSpect source is online. It can be found at: https://github.com/joostvanstuijvenberg/IntROSpect
Please expect lots of refactoring and other changes in the coming months 
IntROSpect 1.0.0 is available in the Google Play Store. It still has limited functionality but at least you can set the refresh rate, which is especially nice if you use resource-constrained devices (like the Raspberry Pi 3s that I use myself).
If you can, please help me! I am trying to persuade my employer to allow me to dedicate some time to the development of IntROSpect. It would seriously help me if you would send me an action photo of your ROS system and IntROSpect together! This will help to convince them that there is actually an audience for this app and the development effort (and time) is well-spent.
Cheers, and happy 2018!
Joost