Well, I couldn't be bothered scouring Simba's source to find the correct place to put all of these in and then export them, so I decided to create this!
Basically, it can do the following:
- Custom random seeds.
- Can update/change the random seed (only really needs to be done once per script). (call Randomise)
- Semi-true randomness (connects to Random.ORG to get a good, random seed value).
- Can force Simba to use this library instead of its own (forces SRL to use it as-well if included first)

I will be using it in my scripts
(harder for Jagex to catch me if they can somehow generate the exact same seed value created at script execution <- PARANOIA!) 
Properties/Methods included:
PHP Code:
PROPERTIES:
randomSeed (unsigned integer) - The actual seed value. It is advised to
use the method SetRandomSeed to set a seed value.
METHODS:
SetRandomSeed - Modifies randomSeed to a user-entered value.
RandomiseWeb - Connects to Random.ORG to set a 'true' randomSeed value.
Randomise - Changes the randomSeed value to the current operation time
of your operating system.
Rand - Returns a random value between 0 (inclusive) and N (not
inclusive). See Random() documentation.
RandF - Returns a random value between 0.0 (inclusive) and 1.0.
RandRange - Returns a random value between two specified values.
Anyways, enough with the chit-chat, here you go 
Save to: Includes/Random.simba
File is attached.