I don't have an Android device to test this on, but you should be able to do this with CSS media queries, e.g. within your CSS file.
p {
font-size: 14px;
color: #c00;
}
@media
(-webkit-min-device-pixel-ratio: 1.25),
(min-resolution: 120dpi){
p {
font-size: 16px;
color: #0c0;
}
}
@media
(-webkit-min-device-pixel-ratio: 2),
(min-resolution: 192dpi){
p {
font-size: 20px;
color: #00c;
}
}