It is a clear "yes!" BJJ can be used both in stand-up or ground fighting. It is an extremely effective martial art. It's versatile, efficient, respectful, and it respects the opponent.
Although it may seem obvious, BJJ training can develop the shoulders, triceps and biceps. Particularly, the biceps or triceps are used in submissions and other elements of wrestling such as transitions and sweeps.
Karate focuses on punching and hand-based strikes while Taekwondo is focused on striking combinations. Jiu-Jitsu focuses on subduing the aggressor or opponent. This can be done using wrestling-style takedowns or position holds, or in extreme cases, submission attacks.