Checkbook.cash is a dApp built by Kui Wang, lead dev of SmartBCH. The purpose is to imitate paper cheques, but it's a powerful tool that allows for many applications, like themself explain. And one of these applications is voting:
On-chain governance is very common for DeFi nowadays. Token holders can vote to decide some issues. But there are a lot of tokens without built-in governance support. As far as we know, the $CATS, KTH and ARG tokens on smartBCH does not have governance support.
For these tokens, blockchain cheque can be a universal and lightweight voting method. For a given issue, just pick an hashed address which nobody owns its private key. Then the holders can send cheques to this address, attaching different tags to support different options. At a predefined moment, the holders together check the accumulated token amount sent to each option (tag), and the option with most token wins out. After this moment, the cheques expire and the voters can take back the tokens by revoking the cheques.
Implications for SmartIndex
Allowing voting earlier in the road map will bring more trust and thus new investors. Although Checkbook is not designed ad hoc as a voting platform, it's easy enough to use and a tutorial will be written to help $SIDX holders to make and vote proposals. The main difference with the off-chain voting platform is that voters will have theirs tokens locked during the voting period (variable, 1 week by default). This can be seen as a disadvantage, but on the other hand, just people which hold $SIDX long term will vote.