Multisignature Contracts are one of the top features offered by NEM. Easy to use and well designed, it allows you to secure an account by requiring multiples signatures to validate a transaction. When an account is converted to multisig, nobody, even his creator, can initiate a transaction directly from it. Only accounts designed as cosignatories can do it.
You can even use M of N to require the number of signatures you want among the total cosignatories. For example, you have 4 cosignatories for an account, you can choose to validate a transaction with only 3/4 or 2/4 signatures. Also, on chain notifications give almost instant appearance of a transaction requiring signature on the blockchain, it will be really useful for what we're going to do as all automated cosignatories can now communicate only through the blockchain.
Multisignature Contracts are the first “on blockchain” multisig solution. This doesn’t sound like a big deal at first, but if one really takes a closer look at it, the advantages are significant. With other platforms, multisig has always been client or wallet based which means each implementation is not compatible across many different platforms, even if it is of the same crypto currency. NEM’s multisig can work with APIs and any wallet or app connecting to the NEM chain. This even enables blockchain pushed notifications announcing transactions to the wallets to sign.
NEM’s version of multisig doesn’t make new accounts for a multisig address by combining keys, instead it makes a contract that assigns rights and powers of a certain account to other accounts. This form of multi-user accounts can make any form of M of N with ease and can also have the M or the N edited just as easily by simply just updating the contract on the blockchain. And since the NEM’s multisig contracts can be edited as many times as a person likes, either adding or subtracting people as needed, it is not only good for securing funds, but also makes for a good foundation for DAOs (Decentralized Autonomous Organization).