There exist implants that interface with nervous tissue for input purposes either via nerves or sometimes lately as "cortical implants". This stuff comes up around visual prosthetics and cochlear implants.

My understanding is that this is an area of active research for helping people with sensory disabilities, and that the issues that tend to come up have to do with input resolution that its "good enough" to get along, and (especially with vision) the decrease in expected lifespan of individual neurons and nervous tissue after being put in close proximity to electronics.

Sharp, hot, electrical stuff is frequently "ouchy"...