There may be programs out there that might help, but in my experience the best way is just to sight-read as much as you can. There's no magic bullet that makes you a better sight-reader, it's just good old fashioned hard work and practice, practice, practice.
I'd suggest getting some volumes of easy pieces and then sit down and sight-read one a day. Don't do them too much - if you do that you'll end up memorizing the piece and then you're not practicing reading anymore. Some examples of volumes to try might be Schumann's Album for the Young, Bartok's Mikrokosmos, Bach's little preludes, Bach Chorales, Gurlitt Albumleaves, etc...
When you sight read them, don't just plow into them. First look at the piece for a minute or two to learn as much as you can before touching the keys. Look for things like tempo, key signature, time signature, and the general melodic and harmonic ideas. Then try to play it. When you try to play from sight, go as slow as you need to hit the notes correctly, and do not stop to correct mistakes.
You don't need to do much of it at each practice session, but make sure you do a little as part of every practice session. I made sure to do at least 5 minutes a day of sight-reading, and it has worked wonders for me. As for the computer programs, they don't seem like they'd work (for me at least). Learning to sight-read is something you do at the piano, not in front of a computer screen. They may have some usefulness, but in my experience, there's no substitute for just rolling up your sleeves and doing it.
What you are is an accident of birth. What I am, I am through my own efforts. There have been a thousand princes and there will be a thousand more. There is one Beethoven.