This is something I would have done myself a long time ago if I wasn't such a crap programmer. This runs reasonably fast even on my nearly six year old Macbook even in Safari. It has equirectangular* output and 8-bit land-only elevation output as well.
Development is ongoing, and Mr. Davidson seems to be responsive to suggestions.
I have a blog with a very basic tutorial on the use of the program.
Astrographer - My blog.
-How to Fit a Map to a Globe
-Regina, Jewel of the Spinward Main(uvmapping to apply icosahedral projection worldmaps to 3d globes)
-Building a Ridge Heightmap in PS
-Faking Morphological Dilate and Contract with PS
-Editing Noise Into Terrain the Burpwallow Way
-Wilbur is Waldronate's. I'm just a fan.