[Landstander]

From what I understand, TempoUp and TempoDown currently give you a range of 0.75x to 1.55x (with some possible future changes coming), although it reads on my display as .8x to 1.5x since there is only 1 decimal place in the OSD.  So you do have Slow motion with sound already available.

It is thanks to TinyHands that I was able to capture the remote key.  Using the KeyMap addon you can set up the remote buttons to something you'll remember, and then either using ES File Explorer, or like I did, the BackUp addon to dump the gen.xml file to a removable device for editing.

From there you can see what the keyid is for the remote button.  For example I found <key id="61568"> is "Up Arrow" on my remote.  You can then set it to a custom function like PlayerControl(tempoup).

If you don't want to steal any buttons like directions or FF/Rewind, you should be able to use the modifier mod="longpress" such as:

Code:

<key id="61568" mod="longpress">PlayerControl(tempoup)</key>
<key id="61569" mod="longpress">PlayerControl(tempodown)</key>

In theory that would keep up/down arrow function normal (BigStepForward, BigStepBackward), but long pressing the button would give it the tempoup/tempodown function.  (Although I think the opposite configuration might be more intuitive.)

I don't know anything about frame advancing though.  I haven't tried to assign what you suggested.