A device, system and method for temperature-based lesion formation assessment and mapping functionality using an accessory usable with an over-the-wire balloon catheter. The device may include a first annular element, a plurality of wires coupled to the first annular element, and a second annular element, the plurality of wires passing from the first annular element through the second annular element and into an elongate wire conduit coupled to the second annular element. At least one of the plurality of wires may include at least one temperature sensor and/or at least one mapping electrode. The first annular element coupled to an outer surface of a sheath. As a balloon catheter is advanced out of the sheath lumen, the distal tip of the catheter engages the second annular element and pushes the wires out of the sheath lumen, everting them over the balloon of the catheter.