On iOS devices, Apple uses a Detail disclosure button for additional details that are aside from the main list navigation. The image below is taken from the iOS HIG.
Another example of this can be seen in the "phone" application on iPhones.
As this icon is iOS specific, I don't want to use it for non-iOS applications. What alternative icon would you use for detail disclosure in a web application that will be used on iOS, Android and Blackberry devices?
It's a pretty commonly used icon for "click to show more"; not the exact icon but the guillemet going outward in some form of icon. A guillemet on it's own tends to indicate the whole row is clickable but making it "look" like an icon suggests that specific area is clickable. Trying to be too different is if anything more harmful than going with the standard.
It's also important to note that the actual term "detail disclosure indicator" is a term invented by Apple just for their own HIG; no one else (to my knowledge) has such a rigid structure for what icon means "next hierarchy level" and which means "show me this detail", thus you're not going to find the explicit items Microsoft and Google require for this purpose because they don't exist; your best bets are what icons common apps for either (or all) platforms use which are also applicable to your use.
Another common, possibly more common pattern is the chevron pointed down to indicate "click here for more details" (and often pointed up to mean "hide details") This is youtube's:
A plus sign is also fairly common in web apps to mean "expand" but this could also be confused for "add item" or similar meanings depending on context.
I have seen similar examples on some android apps, but I don't think this is particularly well known interaction for android users.
Can you have different versions for iOS, Android and Blackberry? I found some research that shows users try to use the Android hardware button to access such information.
How about just > ?
