The Good Doggie Position is a great way to explore different sensations and what feels good to you and your partner. The person sitting on top can grind against their partner's genitals while using the toy or reach between their legs and massage their partner.
Using a versatile toy from Lion's Den like the Tryst Bendable Massager means there are tons of possibilities for fun. It isn't built to be specific for either penises or vulvas, but it works very well on all kinds of bodies...including on nipples if you enjoy some stimulation there!
The Good Doggie doesn't require much mobility, particularly for the giving partner, as the partner on top is primarily responsible for the action in this position. Wheelchair users and people who have difficulty balancing or standing for long periods may find this position more enjoyable than others.
As always, discuss your likes and dislikes with your partner as well as what your body can comfortably do.