I know there's bipedal for animals that have 2 legs, but what of animals with 2 arms?
Well, logically using the Latin roots, the word would be either bibrachial or bimanual. Brachium is Latin for "arm", and manus is Latin for hand. In my book the distinguishing feature of an arm is that it has a hand (manipulation mechanism) at the end of it, so they are basically the same. But whatever works best for you.
Bimanual does seem to exist in some dictionaries. However, the definition seems to be more like "something that requires (a human being) to use both hands to operate".
I think in certain very specific circumstances (e.g. a biology paper) it would be acceptable to use it anyway, as long as you define it for your readers up-front. If that will make things clearer and more succinct in the long run, it'll be worth it.
Just be really careful about not using that word in realms where it already has another meaning (which from my searching seems to be mostly power-tool operation and certain medical realms).
Alternatively, you could use something like bibrachial. It seems to be a much more obscure word. This makes sense, as lot of folks can work out that "manual" is related to hands because it actually has that as an English meaning, but brachial isn't really used in English to talk about arms much. It also appears to have an existing medical meaning which I'm guessing (I am not a doctor) amounts to "in both (human) arms". So the same caveats apply.
But since manual is Latin for "hands", brachial is probably better if it is really arms you are after.
I'll ignore things like octopuses and starfish.
Tetrapoda is the taxonomic group of four-limbed animals. Not a particularly useful term after the Permian extinction, since after that pretty much all animals with limbs had four. It's just a matter of whether you call them all "legs", or call two of them "arms".
As @Saeed Neamati says, the main reason we don't have a word for "two-armed" is because there ain't no such animal. Apart from primates, who are to an extent defined as such (though I'm not completely comfortable calling a loris's forelimbs "arms").
You might call a squirrel's forelegs "arms", but that's a bit metaphoric/anthropomorphic to me.
TL;DR: Animals with two arms are called Primates.
In vertebrates, if the front appendages are not used primarily for walking, they will be called 'arms' instead of the usual legs (e.g. kangaroos, primates). Mammals have at most 4 appendages so there's no real room for more than two arms (please ignore clever rodents and flying squirrels).
In insects, spiders, and other animals with more than four appendages, they are all just called legs even if they use them mainly for not traveling.
So there really is no word for it, and the lexical gap remains only in science fiction.
Bipedal doesn't mean animals with 2 legs. It refers to animals who use their legs (rear limbs) to walk. These are really different. We also have quadrupeds that refers to animals who walk on 4 legs. Cow is a quadruped, and kangaroo is a biped.
But now let's enter into physiology. Do you know a kind of animal which walks on it's hands? Because there is no such an animal, there is no name for that.
No external object, no thought of it, no name for it. :)
The answer is simply bibrachial, as TED explains.
Just google to see common use of it.
Bimanual (two hands) is totally different. It means, well .. two hands. It's commonplace that a robot (or vortual 3D 'being' - model etc) can have X hands (or hand analogues), unrelated to the number of arms.