Surgeons currently use small physical cotton, paper, or plastic markers to track the location of functional brain tissue during tumor resections. To address the risk to patient health associated with these markers, the XSpot is proposed as a more precise method to provide real-time feedback about tissue location. The device has an estimated total addressable market of more than $220 million. The team interviewed neurosurgeons and specialists at 14 different hospitals across the nation; personally and virtually observed functional mapping during tumor resection surgery; consulted with electronics and computational experts; and conducted thorough reviews of the literature and prior art. Across device development, the concept evolved to use ultrasonic sensors rather than electromagnetic sensors to reduce costs; mount the sensors on the stereotactic head frame rather than the brain tissue to avoid damage to brain tissue; and include additional features such as different colored indicator lights and a button to remove stored positions for increased ease of use. In the final design, the XSpot is an attachment for the stimulation and suction probe used by surgeons during tumor resections that stores the location of vital functional tissue, alerting surgeons in real time if they are in danger of harming that tissue. Using ultrasonic sensors, the location of the probe is tracked, and audio and visual cues are provided in real time when the probe is near the functional tissue. The device can mark and detect locations as small as 1 cm across and are accurate to 3mm. XSpot can also hold more than 20 positive and negative locations in memory while providing near instantaneous feedback. Envisioned next steps for the device actualization include: more precise location and motion sensors, more efficient reflectors of the ultrasonic signal, and miniaturizing the circuitry.