I saw a demo where the PreSonus StudioOne's Gate plugin generated a midi-note whenever it activated/opened (according to threshold & attack settings).
This is great for MANY applications  - triggering other sampled kicks or bass based on a live kick, triggering a sub-bass synth to add low-end to a live or sampled kick, snare or other instrument. 
Is there any way to do this with a stock SPLAT plugin or any other commonly available plugin?

The Drum Replacer is killer for this application, because you can adjust the sensitivity just like a gate. Although it can do most of what you want without involving MIDI (e.g., trigger a snare, kick, etc.), if you drag the Drum Replacer Region FX clip to a MIDI track you'll have a MIDI note for each trigger. Because the Drum Replacer has three "channels," that means you can have up to three MIDI notes for various triggers if that's appropriate.

If you have X3 or newer, this thread may be of interest. As Craig mentions, the plugin from that thread (ReaGate) can be used to fire only a single MIDI note AFAICT, so it seems rather limited in application due to this IMO. You could, however, choose multiple instances of the setup especially if each audio input (trigger) is isolated to its own track.

Cool...

Being able to pull audio into a MIDI track and have it create MIDI notes is amazingly cool. More flexible than gating IMHO.

Anderton
Being able to pull audio into a MIDI track and have it create MIDI notes is amazingly cool. More flexible than gating IMHO.

more flexible but much more work!

pwalpwal

Anderton
Being able to pull audio into a MIDI track and have it create MIDI notes is amazingly cool. More flexible than gating IMHO.

more flexible but much more work!

Why? A gate responds to transients, Drum Replacer responds to transients and you can filter/set level independently of any gating action per se. For example I sometimes use DR to extract MIDI notes from a guitar chord's initial transient. It's pretty easy to set up, you just create a region FX and drag it into a MIDI track. 
 
 

why? don't you have to re-drag the audio-to-creat-the-midi at every change? (nothing to do with drum replacer!)

When you drag an RFX track that has used Drum Replacer into a MIDI track, it generates notes for however much of the track you bring in based on how the triggering is set up in Drum Replacer. I usually just bring in the entire track, and if there are places where I don't want to generate MIDI notes, I delete them. 
 
You may be overthinking this. It's really easy. Forget that it's called "Drum Replacer"...pretend it's called "Audio Transient to MIDI Note Converter (that just happens to work with drums)."

Thanks, Craig!
Not sure how I missed this.  I think I'm trying to learn way too many things at once to complete my current projects.
 
I'm hoping the new Help subsystem will "help" me out ;-)