I am assuming that you're talking about the Virtual Keyboard API (where a keyboard appears on the screen, tied to a text field, and the user can use the mouse to click keys and input text). If that's correct, then here is the list of layouts that it supports:
Note at the top of the page, though, that the Virtual Keyboard API is deprecated. Per the standard deprecation policy outlined in the TOS, you can expect Google to use commercially reasonable means to maintain the service until May 2014, three years from the announcement. This means that, barring any drastic developments, it's reasonable to assume that it will probably function until May 2014, but Google may shut it down at any time if maintaining the service becomes, in its sole discretion, unreasonable. So you can utilize the API at this time, but it would be wise to be considering alternative options and making migration plans for down the road.
Jeremy R. Geerdes
Generally Cool Guy
Des Moines, IA
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