One's hand refers to digits, penetration refers to the action of penetrating; therefore digital penetration equals shoving your hand in ones cooch.
Dick and Jane went out for an evening of entertainment, little did Jane know, that by the end of the night her cookie would experience digital penetration.
A sexual act involving the insertion of a digital camera (most commonly a Sony CyberShot) into a sexual orifice
"Digital Penetration.... Is that something to do with digital cameras?" - Laura P.