Mr. Handy is good for auto-collecting things or defending the rooms, pets are nice to boost your guys, lunch boxes gives everything (weapons, mr.handy, dwellers, caps, power, etc.). Bad side of lunchboxes is: although you can get pets and mr. handys from it, you will most likely get frustrated because you will probably end up with 500 caps and some blue weapon. I would wait till they fix the balance of lunchboxes before buying them with real money...
Definitely do not buy anything, they are not worth it. Mr. Handy only collects 5k caps in wasteland, then returns automatically. Mr. Handy is extremely slow to collect on rooms ( you end up collecting them anyway), and cannot collect levels. Mr. Handy dies fairly quickly and costs 2k caps to repair. Lunchboxes have an extremely low rate of producing quality items; you would waste tons of money trying to get even a few good things. Pets are cool, but you can get them in free lunchboxes by completing quests. They are not worth buying.
I buy things with real money just to support the developing company. Nevertheless, I kind of agree with Beldanlead. As I said, lunchboxes will most likely make you angry or frustrated.
I admit at first very disappointed in Mr Handy but have grown to really appreciate him defending the first floor - it's nice to have the extra help.
You have to drag them inside your vault first, and then you can drag them back outside to explore. You can only have one Mr. Handy per floor.