Using new back-end (and probably the old one, /mutatis mutandis/), you
can use something like:

(add-to-list 'org-e-beamer-environments-extra
'("onlyenv" "O" "\\begin{onlyenv}%a" "\\end{onlyenv}"))

You can then add an headline above your information and set its
properties "BEAMER_env" and "BEAMER_act" to, respectively, "onlyenv" and
"2-". You can set easily the first one with C-c C-b when
`org-e-beamer-mode' is active.

That's awesome, I will try this.

I am thinking about providing this feature with "ignoreheading"
environments. I.e.,

Sounds interesting but I'm not totally clear on what "ignoreheading" environments are for.

Thanks!