According to what I understand from caniuse you should be able to use linear-gradient on IOS 6 and Android 4.* with one caveat, you need to prepend it with -webkit-
, i.e. you'll want your css file to contain two lines for the background, instead of just the one:
background: -webkit-linear-gradient(rgb( 59, 89, 152), rgb(109, 132, 180)) repeat scroll 0% 0% rgb(238, 238, 238);
background: linear-gradient(rgb( 59, 89, 152), rgb(109, 132, 180)) repeat scroll 0% 0% rgb(238, 238, 238);
Android 2.3 shows 'partial' support, so it might work or it might have issues. My guess is it has a good likelihood as it's straightforward linear gradient.
Also, at some point in the past, the standard for gradient was in flux and there were some different approaches, but again linear-gradient is pretty stable, so just prepending it with -webkit-
will hopefully do the trick.
I haven't tried this on android or IOS myself, but from what I read it should work.