Medary.com

Hmm.  We have Sprint (pity us).  We can see a cell tower from our house, but sometimes our phones can't get signal.  In our house.  And don't even get us started on when we go visiting Filbert's sister up in rural South Dakota, where Sprint service is, to be polite, nonexistent.

Sprint AIRAVE™ is a device that creates a CDMA signal for your mobile phone (like a miniature cell tower). AIRAVE provides enhanced and reliable mobile phone coverage in your house or office even if your existing wireless coverage is poor.

Hmm, again.  Another way for Sprint to extract money out of customers.  Skimp on your nationwide network coverage, then sell folks a do-it-yourself cell tower.  Genius!

Update:  Ars Technica's take:

The potential advantages of the service are obvious, but Sprint isn't exactly giving it away. The Airave unit itself is $99.99 and must be activated when purchased. Customers must also pay a monthly Airave enhanced coverage charge ($4.99), and purchase an Airave plan ($10-20 per month, depending on your plan). The total monthly cost of Airave should run $15-25 before taxes and fees. $15 isn't much, considering you're buying cellular service for an area that (presumably) lacked it, but it's extremely ironic that Sprint is charging users for the dubious privilege of providing their own backhaul.

. . . 

Paying for the right to backhaul over one's personal Internet connection isn't a great deal for consumers, but the benefits of femtocells could easily erase the negatives, especially when it comes to providing coverage in hard-to-reach areas. Deployed en masse, these miniature towers could offer truly ubiquitous coverage, and make random dead zones a thing of the past.