Combine the jamaica, water and sugar in a saucepan and heat to just under a boil. Simmer gently until the liquid is syrupy and infused with the red hibiscus color, about 45 minutes. Strain this liquid through a coffee filter and allow to cool. The liquid can be stored, refrigerated for several days.
In an ice filled shaker, combine tequila, pineapple juice, and three ounces of the cooled jamaica syrup. Shake well and strain into a martini glass. Float the jalapeno slice on top.