Dagger Hiding Bracer (3.5e Equipment)
From D&D Wiki
The dagger hiding bracer is a bracer that does exactly as it says: it conceals a dagger inside.
For the bracer to work properly, the hilt of the dagger must be removed with either a Strength check (DC 18, reflex 10 to avoid taking the dagger's damage as you forcefully ripped the hilt off), or Disable Device (DC 12, no reflex needed, in this manner you take the time & care to actually carefully remove the piece).
After the hilt of the dagger is removed it may be set into the bracer on the underside (so that it is hidden even more by your forearm) with a successful Disable Device (DC 15, if you know how to take something apart, putting two things together isn't that difficult), or Profession (trapmaking) (DC 10, the dagger is set into a complex little system of rods and a switch, with a few gears so that it may spring out when the bracer is activated) check. Now the bracer is ready for use.
As a free action, you may now draw the dagger. The dagger shoots from the bracer with a firm flick of the wrist, and as long as your hand is out of the way. The weapon is held in place by rods within the bracer, and will not fall out or be pushed back in (within reason... It's obvious that a dragon can easily over-power the metal rods working in the device, so it is your judgement call).
The dagger now has a circumstantial bonus to be conceal on your body of +5 (to whatever skill you determine it to be, like Hide or Sleight of Hand). You gain a further +2 bonus to conceal the weapon from an opposed Search or Spot check if the bracer itself is hidden within a loose sleeve (something like skin-tight leather won't work, but a large cape over the shoulder or robes would). Attacks can be made just as if with a normal dagger, and it counts as a light weapon.