Real-time translucency effect
I think you may want to take another look at the iOS user interface if you consider real-time blurs to be out of range of mobile hardware:




Blurs are totally in range of mobile hardware. Yes, you need a fairly large number of texture samples for a blur with a large kernel, but the texture samples are also cached very well, and you can use a separable blur, which effectively means that an MxN blur requires M + N samples, not M * N samples. You can also take advantage of hardware bilinear sampling to reduce the number of samples that your blur requires.