After Bond's escapades in Mexico City, he's suspended from activity duty by M, and as an insurance policy of sorts, he's sent to Q to be fitted with a nanomachine microchip which is delivered into his bloodstream and can track his movements at all times. Bond manages to convince Q to take it offline for 48 hours while he pursues Sciarra's wife Lucia (Monica Bellucci) and follows up other leads, all while Q lies to M about Bond's whereabouts in order to maintain his cover. Considering the high-tech nature of the gadget, it's surprising that it doesn't really figure much in the narrative at all: it's a pretty unnecessary affectation overall, not that it's a bad one or anything. It's just... weird.