I have not personally used this app. I did notice The Penny Hoarder did write about them: https://www.thepennyhoarder.co...-finance-app-review/
For most people who are concerned about connecting their bank account, I would not recommend just doing it unless you are super confident in the company.
I on the other hand tend to test things and am probably not as careful as I should be when it comes to that.
I did sign up for a similar service once but I didn't set up my account properly so it wasn't working... however they did start charging me without my knowledge so I ended up paying like $10 a month for 2 months even though it wasn't actually working.
I would say you are better off just setting up a different bank account and setting money aside, it won't be automated but it's the same idea.