>>>How much local data ?
>>>It might be possible to do this with HTML5 - it has quite a bit of support/ability to work offline and to use local storage.
>>>Advantage being that you'd be better able to support multiple platforms.
>
>Quite a bit of local data,

Not exactly a definitive answer :-}

>the enviroment it will be used in will require the tablet to be used in basements, kitchens, store rooms etc, where Wi-Fi is unlikely to be reliable if it is even available.

>Does HTML5 just use variables or can it link to a local database?

There's LocalStorage (for small amounts of data) and Local Databases. Although W3C decided to deprecate the latter it can still be used on browsers that support it. See:http://hankchizljaw.co.uk/tutorials/html5-local-storage-and-local-databases-tutorial/04/06/2012/

>Can you store and run the HTML locally on the device?

See : http://msdn.microsoft.com/en-us/magazine/hh561712.aspx
You can provide a manifest which controls which pages continue to be available when the device is offline....