No, anyone with a Spiking account can use the app without having a link to a brokerage account. You can set up a watchlist to easily monitor the stocks you love and track your portfolio on them.
However, by linking your brokerage account you are enhancing the ability to trade on your positions. Eventually, you can place orders with your brokerage once the Spikes you set get executed. By linking your brokerage, you are getting access to alternative order types that your current broker doesn’t provide.