Can't start appmon in erlang R17 RC1

appmon looks to have been removed, in favour of the new observer application. See the note here. There seems to be precious little online documentation on why, but presumably the docs included in your erlang installation would at least help you find how to use it.

As noted in sanmiguel's answer, appmon has been removed.

The solution for me was to use this command instead:

observer:start().