You can write a sort of bastardized version that waits a fixed amount of time for the user to write something and then return whatever was written. Alas the real version that waits for the user to type and then returns instantly (with optional timeout) would require preemptive multitasking which isn't supported by Lua and would be one hell of a hassle to implement. I really doubt that this is something that the devs would like to spend time on.
