Top-upable SIM cards in USA?

I and my wife will come to US to live in NY for 2 months. We need US sim cards to communicate between us. In the UK there are networks like Lebara or Lyca whose sim cars can be purchased even from the Heathrow airport through a vending machine at the arrival terminal and all you need is to top up your credit. Calls between the same network is free. It is also possible to top up data.

I'm looking for a similar solution in the US. Free calls between the same company and being able to add data is preferrable but not necessary. We have our unlocked iPhone 5s whose networks are compatible in the US and we're not considering using our home country's sim cards at all during our stay.

There are many options for what your looking for. It does depend if you just want calls, or data and texts.
AT&T go-phone has the most plans. They have:
2c per minute per call
$2 per day,
$25 per month, 250 mins, unlimited text, no data
$40 per month, 500 mins, unlimited text, 200 mb data
$60 per month, unlimited calls, text, and 2gb data.

They have specific stores in the airport that have other sims cards, but since you have a smart phone, these "plans" come with text and data too.

Other pre-plans to check out:
SIMPLE Mobile
T-Mobile Pre-paid
Straight-talk
Virgin Mobile (BEST VALUE, $30 a month for UNLIMITED EVERYTHING!)
Net-10

again, like i said, just find one of the stores in the airport and look at the plans and prices there. But ultimately I would go for Virgin Mobile.