Pour the tequila in a mason jar or other container and add the habanero. Let steep for about 3 hours (you can leave the habanero in longer, but beware that the tequila will get spicier and spicier the longer it sits).
Place sea salt on a s mall plate. Brush rims of glasses with water or simple syrup and roll to coat in sea salt. Fill glasses with ice.
Divide grapefruit juice between glasses (using ¾ cup for each). Pour 2 oz. habanero tequila into each glass. Stir. Garnish glasses with lime and grapefruit wedges if desired.