Bottom SPST switch is a small reed switch mounted on small wood block and mounted to bicycle front fork with "U" bolts so it will not interfere with bicycle brakes and can be removed to service tire. Maybe, covered with black electrical tape for improved appearance. Epoxy two magnets (180° apart on wheel rim), as type used on magnetic cabinet door closures on tire rim top where brake shoes will not be hitting magnets. Have about 1/4 inch clearance between magnets and reed switch.
Rig flashing lights or speedometer circuit from wheel switching circuit.
