Indeed the slave eye does very effectively mimic the SB900's multiple flash stroboscopic mode (RPT mode in the flash menu) it certainly works just as well with any other cobra type flash unit out there.
Here's a test i did over the week end using and Einstein unit in an umbrella and accenting the background and cymbals with an SB600 and an old Norman flash head connected with some Radio Controlled trigger. Using those until i get a set of Pocket Wizard triggers. For this picture the SB900 flash was aimed outside the scene just to act as a multiple flash triggering device.
[url][url=http://www.flickr.com/photos/sargentray/8628633223/]

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Portrait drummer 1B Mod Final LR TXT LR-5663 par
Sargentray, sur Flickr[/url]
Be gentle with the model please as it is an auto portrait using the intervallometer function of my Nikon D3s.