Deeper sonar bobber questions

So folks I'm a shore fisherman but thinking about getting a little boat (2 man or maybe kayak) and wanted a sonar.
So I notice they have these sonar bobers that hook up to your phone now. They don't seem to go as deep as boat mounted units but how deep do I need? I'd be in creeks, the Osage river and Stockton lake.
Most of the time I hear the depths they are fishing in the lake is 10-20-30 feet. That's well within Deeper's 150 foot range, is that enough? Do I really need more?
Any one used this or one of the others??

I fish out of canoes a bit and I built myself a portable unit by getting one of the $99 ones, (a Bottom Line - no longer made) - mounting it on a plastic box with a 12V drill battery in the box and using tye-wraps to attach the transponder to a block of foam. When I got underway I just threw the the foam block in the water. It gives me depth and surface temperature which is all I wanted. I use mine in both my canoes, my 10' jon boat and while I haven't tried it yet I could take it with me in my belly-boat (float tube).

Oh - and about the ones that use your phone - I don't know about your phone but mine is NOT waterproof or even resistant and is horrible to try to read in the sunlight.

That depth range is just fine for you. However, I don't think I'd want to jeopardize you phone that way. Instead, you can go on Craig's list and find a regular used B/W unit for well under $100.00. Even Cabelas offers inexpensive 2D sonars for that price. Cabelas also offers clamp on transducer brackets you can easily attach to any vessel. They even offer small 12V batteries for this purpose. Here's my set-up:

Attachment 231720

I thought I had pictures of my setup but it took me a while to find them.

Here is the unit as I use it. The battery is in the box with all the excess power cord.

Attachment 231757

And here is the float for the transponder. I have since made a much smaller float.

Attachment 231758

Very nice Clint, that works right there.

I really like the clean look of the battery (shoe) box should work well on my 12ft Jon.