I've updated the Cortexatron online die roller to adapt its interface to smaller screen sizes. I'm hoping this makes Cortexatron more friendly for mobile devices. If you don't have a pile of polyhedrals with you, but you do have your cell phone and a signal, you're ready to play Cortex.
I've also added a randomness report which is available from a link on the bottom of the main page. I'm including this both as a diagnostic and as a demonstration of the system's randomness. Ideally, Cortexatron's die rolls should be uniform and unpredictable. Uniformity is only visible over a large sample size (several hundred die rolls) and as the system accumulates die rolls, the randomness report should demonstrate a uniform distribution of results.
I'm fairly confident that Cortexatron is producing die rolls at least as uniformly as the dice you have in your gaming bag, but if you find that's not the case, let me know and I'll look into it.