For those who don't understand how the Aereo antennas work or who haven't bothered to visit their website and see what they have to say - yes - each account has its own unique antenna, about the size of a dime. So how do they claim you'll get HD reception? Simple. They install your receiving antenna in a location that's very close to the broadcast antennas! With the amount of radiated power at that distance, you probably could pick up a strong HD signal with a paper clip.
The difference is that your viewing device is connected to that antenna you're using with what one could call the EQUIVALENT of a very loooong coax cable. Only it's not a cable. The broadcast is streaming from your antenna to your device over the Internet, whether through wifi or via a wireless data plan.
Currently it's not the greatest in terms of variety. In the markets that Aereo currently operates, subscribers are able to tune in a couple dozen channels, including the local stations for the major broadcast networks, a bunch of lesser entertainment freebies, weather, home shopping, some second language stations and Bloomberg Business.
Wireless can be spotty, depending on your carrier's bandwidth and local signal anomalies. Moreover, if you use wireless streaming a lot, you'll be consuming a helluva lot of data from AT&T or Verizon or whomever you have an account. You're next monthly bill could come as a big surprise. But for those who absolutely have to watch Days of Our Lives on their smartphone or tablet while gobbling down that lunchtime BMT at the local Subway, Aereo may be the answer.