Not sure if the Sling box will work for this, but am very curious to hear if it does. As for an Indoor Antenna, i have tested all the major brands and one outperformed them all: The Leaf Antenna. To learn more read: "HD without Cable - Using an Indoor Antenna" http://www.killthecablebill.com/hd-without-cable/
The leaf is also the number one selling on Amazon if that tells you anything and KilltheCableBill offers $5 off and free shipping.
Since the SB-HD Pro does have a built-in tuner, then you most certainly should be able to get all of the "over the air" channels that are available in your area with just an HDTV antenna plugged in to your SB. Websites such as http://www.dtv.gov/stationlist.htm would be one place to start to see what types of channels will be available -- unencrypted and transmitted in the clear -- in your neighborhood.