I found a very nice video for a (blender internal) shader setup for fake SSS. With a bit of modification its quite easy to make this work in BGE. To make it work you need an additional b/w texture that defines the depth of the SSS effect. In my case, i have 3 RGB files: 1 color, 1 normalmap and 1 file with the specular map in the red channel, AO map in the green channel and subsurface scatter depth in the blue channel. I use a separate rbg node to get the different channels separated.
my node setup for diffuse and SSS (spec is separate and just added on top of this output):