PhotoSounder is a downloadable app. 

***The principle is to create sounds FROM an image.  The tool has adjustment settings that allow you to manipulate the playback frequencies among other adjustments.  It can also reduce noise and do standard sound editing.  However, what makes it interesting is the photo-to-sound feature.  Though the sounds themselves are not that interesting, it can be used and mixed in creative ways adding diversity to a soundscape.

Demo is free, but it puts distortion in the playback, The full version can be purchased for $59 on photosounder.com

The tool is not very impressive for complicated images, but is interesting in patters, symmetry and with fractals.  Complicated, dark images tend to be noisy.

examples:

http://www.youtube.com/watch?v=W8MCAXhEsy4

http://www.youtube.com/user/Photosounder#p/u/13/S64FROErFYA

*most interesting feature* (soundscape stretching) of HAL:

 http://www.youtube.com/user/Photosounder#p/u/15/zTi_HwdlJ20 (wave form of HAL, played back different ways)

Sound can be adjusted in several ways: pixels Spray Width, Intensity, Min. Frequency, Max Frequency (*), Frequency Scale logarithmic Base, Volume, Pixels/Second Time resolution (*), Gamma, Horizontal flip, Invert, Vision Mode, Mask Invert, Rotate etc. 

From: http://photosounder.com/

The following is a non-exhaustive list of what has been found that can be done using Photosounder.

• Turning a sound upside down (bass sounds become treble and vice versa)

• Complex soundscapes using extreme time stretching

• Creating instruments graphically and arranging them into a beat

• Transmitting photographs through sound

• Performing operations between different sound files, such as subtracting an instrumental from a song to isolate vocals

• Isolating or removing an instrument from a complex sound

• New effects such as piano chorusification or time-pixelation of sound

• A new take on more classical sound effects such as sound reverb

• Highly quality and flexibility processing such as denoising

• Creating new sounds from photographs or fractal images

• Vocoding

• Synthesizing spectrograms created from other spectrographs, such as printed spectrograms of bird calls in books

• Pitch shifting, pitch interval stretching, sound rotation, time-frequency domain compression