This is a custom Maya viewport menu, you can create your own if you like
This menu is just pointing to the python scripts and executes them
It would have the same effect as running code in the script editor
Regarding your problem, you do not need any special scripts for that.
If you have a mesh and you need to select inner vertices ( which are closer to bones ) :
1) Duplicate the mesh
2) Select the edge loop that separates inner and outer sides and delete it ( on duplicated mesh ). Then also remove the outer side. After this you should have your original mesh and duplicate of the inner surface.
3) Select mesh then inner surface
4) Go to Ziva Tools, on the very bottom - Select Vertices - click on the option box
5) You will see this UI
6) Change radius to a small value like 0.01
7) Click select
Even this method contain quite a few steps it's quite fast to execute after learning.
Hope this helps !