Mechanics question regarding Hide/Move Silently

[ZomboRobo]

In 3.5, would using an item, specifically a power stone with a material manifestation, give away the location of an already-hidden opponent? I've searched the rules of the SRD and only discovered information pertaining to making attacks giving away one's location, but I've always worked under the assumption that spellcasting and other standard actions would also reveal a character's location and require another check to be made.

If it ISN'T required, then what types of actions *can* someone take without compromising their hidden position?

[Cog]

You'd have to make the concentration check to manifest the power without displays; likewise, a stilled, silenced spell wouldn't give you away either. Either of these are negated if you're firing off some sort of visible ray or the like as a result, though - so something like a Magic Missile would still blow your cover, for example.

If you had to draw the power stone first, that'd call for a Move Silent check as well.

[ZomboRobo]

What if the power is being manifested through a power stone and no Concentration check was made to avoid the display?