I have developed an application to use with my gaming group, with different modules that manage character creation, leveling up, adventuring, inventory, and character sheet.
All can be run from a Windows PC, and everything but the leveling up can be accessed via web browser, so no worries about iOS/Android/Windows.
Also, the character sheet module is specially tailored for mobile devices, and updates the player with info on stun, bleeding, remaining hits, etc, and also shows the description and parameters of all known spells.
The GM application resolves all spell casting, attacks, criticals and skill rolls according to the tables.
I contacted Thom 2 months ago about it, but I am still waiting for a response.
Mind you, the system has potential for RM2,RMFRP,RMU, but it is currently more dedicated to solving things the way that my group prefers, and before I could release it as a commercial (or even free) product, it would require some tweaks to make it more useful for a larger audience.