Cut the limes in half from end to end. With a sharp knife, carefully cut around the inside of each lime and then scoop out the flesh. Remove the membrane from the inside of the lime peel.
Line a 12-cup cupcake tin with foil. Place a lime half, cut-side up, in each cup.
Empty the package of gelatin into a medium bowl. Pour over the boiling water and mix well, making sure the gelatin dissolves completely. Whisk in the club soda and citrus vodka, skimming the foam if needed.
Pour the gelatin mixture into each lime half. Refrigerate until set, 2 to 4 hours.
When set, cut each lime in half to make wedges.
To make orange wedge gelatin shots, use orange-flavored gelatin and substitute tangerines for limes.