The Incandenza Bypass is a simple, low parts count, relay-based true bypass circuit designed by Steve Demedash. It uses a normally open momentary SPST footswitch triggering a simple 555-based flip flop circuit, triggering a non-latching DPDT footswitch. The layout below reflects the pinout of the either the Takamisawa NA5W-K or Omron G6S-2 relays. These are 2 relays I had in my parts stash that worked with the circuit when I breadboarded it and are both rated at 5v. Other non-latching relays can be used, but double check the pinouts and compare datasheets. Schematic can be found here.
Note: Send goes to the effect input, Return goes to the effect output, In goes to the input jack, and Out goes to the output jack.