Extracting the hidden text off an image embedded with steganography
Yes, you can write a single application to reveal the hidden information as long as you know the method and they are not encrypting the messages they hide. The Wikipedia article in Steganography tools lists some information about availability as an opensource, their methods, and usege of encryption. And some information can be found on their website. 

For example, QuickStego says that; 


  The QuickCrypto steganography function allows carrier files to be photographs, drawings, images (.jpg, .gif, .bmp file types) and sounds (.wav and .mp3 file types). Any type of file can be hidden within these types of carrier files. Files and text to be hidden can easily be encrypted prior to hiding if required.


and SSuite Picsel


  SSuite Picsel secures all your text messages using Steganography encryption... 


If encrypted you must know the encryption algorithm and the key to decrypt the message after you retrieve the hidden messages.

There may be also a patent problem since the SSuite Piscel is a company. They may have some patents on the steganographic methods. You may write your software by reverse engineering their products, but distributing it; may cause legal problems.