whats the rarest/most valuable pokemon i can find using the pokeradar
well, there really is none. there are some pretty rare pokemon you CAN find using the pokeradar, but it's all up to you if you like the pokemon or not.
the pokeradar sometimes consider rare pokemon based on the location. for instance, the route south of jubilife, bidoof is considered a super shaky on the pokeradar.
I don't think it's that the Bidoof is considered a super shaky, it's that even in the super shaky grass (where you have a higher chance of catching a Pokeradar-only Pokemon) you can still catch the local pokemon. Which in your case, Bidoof is one of the local pokemon south of Jubilife.
Catching Pokeradar-only pokemon isn't as hard as I first thought. Basically use it and go for the super shaky grass only. If you run into it and get a local pokemon (like that bidoof), just used the pokeradar again otherwise you'll keep chaining that stupid bidoof. Usually the pokeradar-only pokemon show up in super shaky grass 20% of the time, so it may take a few tries to get them. But they do show up eventually.