Watch of Armor (D20 Modern Equipment)
From D&D Wiki
A magical watch that provides an equipment bonus to defense. What did you expect? It occupies space on the body as a magic watch or bracelet.
The defense bonus ranges from +1 to +4. The purchase DCs are as follows: +1 DC 28; +2 DC 32; +3 DC 36; +4 DC 40. Any given version can be upgraded by a mage or techno mage to the next best version for half of the purchase DC of that version.