Preheat oven to 350 degrees F. In a food processor, combine pretzels and sliced almonds; cover and process until finely crushed. Add butter; cover and process until combined. Press pretzel mixture on the bottom of an 8- or 9-inch springform pan. Bake for 8 to 10 minutes or until lightly browned. Cool on a wire rack.
Place the water in a small saucepan; sprinkle with gelatin (do not stir). Let stand for 5 minutes to soften. Cook and stir over low heat until gelatin dissolves; set aside to cool slightly.
In a large bowl, combine cream cheese and powdered sugar; beat with an electric mixer on medium speed until smooth. Beat in sour cream and almond extract. With mixer running, beat in gelatin mixture. Fold in whipped topping.
Spread the filling evenly over cooled crust. Rinse blueberries; gently place atop cheesecake filling. Cover and freeze cheesecake for 6 to 24 hours or until frozen. Run a long sharp knife around edge of cheesecake to loosen; remove side of pan. Let stand 15 minutes at room temperature. Cut cheesecake into wedges.