A novel finger-sensing nanocomposite with remarkable and reversible piezoresistivity is successfully fabricated by dispersing homogeneously conductive graphite nanosheets (GNs) in a silicone rubber (SR) matrix. Because of the high aspect ratio of the graphite nanosheets, the nanocomposite displays a very low percolation threshold. The SR/GN nanocomposite with a volume fraction of conductive nanosheets closest to that for the percolation threshold presents a sharp positive-pressure coefficient effect of the resistivity under very low pressure, namely, in the finger-pressure range (0.3-0.7 MPa), whereby the abrupt transitive behavior of the nanocomposite is accounted for by an extension of the tunneling conduction theory which provides a good approximation of the piezoresistive effect.