There's nothing really restricting where you install various pieces of 'ware; the labels, 'bodyware' and 'headware' are more a suggestion. It's popular, for example, to install a smuggling compartment in cyberlimbs.
That said, others are somewhat explicitly limited. Can't rightly install a tooth compartment in your toe. (That said, I'd totally let someone install a fingertip compartment in their toe. Especially if it had a monofilament whip inside.)