What is "Key Splitting"? When would I use it? Here is some github code to create split keys.


Is Key Splitting the same as Multi Sig?  
What are the benefits of Key Splitting, what's it used for? 
How does it relate to P2SH or any other relevant BIP?
How are split keys used in a transaction?
No. Multisignature transactions involve multiple keys/signatures, whereas this involves splitting up one key.
As far as I know, it's not used at all in production. There are a whole host of issues.
P2SH was created to make multisignature transactions easier to implement for e-wallet providers and merchants, and to move the burden of multisignature transactions from the sender to the reciever.
Like so:


Generate a key
Split the key up, store the pieces in different places
Put the key back together
Sign transactions


The major problem with split-key transactions is that you need a trusted third party. When they generate the key, they could secretly store it. When they put the key back together, they could secretly sign a transaction that stole all of your bitcoins.