Sprint just released their Airave box, which works like a miniature cell tower (covering 5000 sq ft) anywhere you have a broadband connection, with the added advantage that all calls that go through the Airave box can be completely unlimited. It requires an existing Sprint voice plan plus a DSL/cable modem connection, but it supports up to three calls at one time, with a charge of $100 for the box and unlimited calling using the Airave for $15/month for one line or $25/month for multiple lines. It even will automatically transfer a call from the Airave box to the Sprint network (if available) when you leave the Airave coverage area.
They don't point this out, but I also don't see a reason that you can't take this with you when you travel and have unlimited calling wherever broadband is available (Edit: it may work only in the US/Puerto Rico, see scoobydooby's post below). It's basically VoIP that uses your existing Sprint wireless phone.
Alternately, if you just want the box to provide Sprint coverage where it's either nonexistent or spotty but you don't want to have unlimited calling, it's only $5/month.
Edit: This works with ANY existing Sprint wireless phones, unlike T-Mobile @Home which requires a landline phone, or T-Mobile Hotspot calling which requires special wireless phones.
It will be available at Sprint stores starting August 17.
