1. Belly protection - Being pregnant while having an older child in the house is wonderful and magical. That older child really gets to interact with your growing belly. However, toddlers/preschoolers are accidentally dangerous. They don't mean to kick/punch/headbutt your belly, but it happens - and you fear every time that a little tiny person is going to fall out of your uterus. Pregnancy Kevlar vests or something would be a great idea to wear around the house.
2. Extend-o arms - I know that there's no way to really make your arms longer, but it would be nice if there were some sort of hook or something that could help you put on socks in the morning, or clip/paint your toenails. There's a certain point in pregnancy at which you just sort of think, "Eh, flip flops are fine, even if my toenails look like a wild animal's."
3. Belly rearview mirror - I'm not sure how else to say it, so I'll just go for it. After a certain point in pregnancy, personal grooming becomes a guessing game. Please take this poorly-illustrated cartoon as an example of a pregnant woman's field of vision.
So clearly drawing hands and faces aren't my thing.
That grey area is the area that a woman can see effectively when she's looking downward. Anywhere from the belly down pretty much becomes a mystery. You could be growing a goiter on your upper thigh and have no clue (I know that's not medically possible, but stay with me here). If there were some way to attach a rearview mirror to a belly belt or something so that you can see what you're shaving, it would certainly make things easier. I don't know many people who love going to weekly OB appointments with unruly body hair all over their lower half.
4. Food-o-meter - I think I'm fairly well on-top of what you're not supposed to eat when pregnant. Anything lunch meat-y, fish with mercury, soft cheeses, caffeine. Wait, there's also herbal tea, alcohol, raw vegetable sprouts, sushi, and more, you say? Wouldn't it be nice if there were some little sort of food-tasting device that you could put a little bit of the food in question into, and it would tell you if some sort of baby-harming bacteria or chemical is in it? I suppose a phone app is probably more practical, but sometimes you are really craving that roast beef sandwich and want to know if "just this once" will hurt things or not.
There are lots and lots more, but these were just the ones that came to my mind based off of my last 24 hours of pregnant existence. I would give any of these the most positive review ever.