Focus Band

An item that has a 10% chance of protecting your Pokemon from fainting with a remaining 1 HP. Its other effect is that it may protect you from multiple hit moves like Icicle Spear or Tri Attack.

Locations
G/S/C: Saffron City

R/S/E: Shoal Cave or Battle Frontier (Emerald only)

FR/LG: Held by wild Machokes sometimes.

D/P/Pt: Battle Tower/Frontier for 48BP.