Why is that only possible in Pharo? The concepts seem pretty language agnostic. Maybe I've mis-understood what it does but I can imagine a devtools plugin for Chrome/Firefox that basically does effectively

    if (x instanceof foo) ShowUIForFoo
    else if (x isnstanceof bar) ShowUIForBar
    ...

And then let you register your object UIs so they show up in the debugger.

Thanks for sharing. I'll explore it.