I have a BlueDriver I used to *GET* information on my old Prius, but that unit would not let me change customization settings needed to handle the backup beep. That's why I got this much less expensive but capable interface.
When I got a new Prius Prime to replace my 10 year old Prius I expected I could turn off the backup beep (in the cabin only) the same way: with a combination of button pushes. But NO! I had to access customizations via the OBDII interface.
I found a bunch of info on the internet and some of it plain wrong. I'll outline the steps to access the customization that worked for me on my Prius Prime. These should work on any gen4 Prius.
PLUG IN THE TONWON ADAPTER
Find the Prius Prime's OBDII connector. It isn't under the dash near the center of the driver's seat like many other Prius I've looked at. It's above the parking brake. Plugging in the TonWon adapter is simple and easy. Mine lit up even before the car was turned on.
INSTALL CARISTA APP
I tried OBD Fusion suggested for this use without luck. I ended up using Carista. The base app is free on the iTunes store and while following the process I needed to make a $9.99 in-app purchase. More on the purchase later... It is also available for Android but not from the Amazon App store.
CONNECT TO TONWON WIFI
The TonWon WiFi adapter has a network name (SSID) of V-LINK. This is an open network (no WiFi key needed). You will need to go into settings on an IOS Device and connect to the adapter.
LAUNCH CARISTA & PREPARE THE CAR
Once WiFi is connected you can launch the Carista app and turn on your car in *accessory* mode. You'll get a screen offering Diagnose, Customize and Service. To change the backup beep setting I used the "Customize" option.
CONNECT CARISTA TO THE TONWON
Carista will ask what kind of adapter and you should select the WiFi ELM327 adapter. Carista will search for the adapter and then download all of vehicle information and settings. This can take a minute or more, so be patient. The progress display was informative.
CHANGING SETTINGS, PART 1
When settings are loaded you'll get 3 more options: Doors/Windows/Remote, Instruments/Display/Dings and Lights. I selected the one with "Dings" :-) and got a screen with a bunch of options. The one I was interested in is "Reverse-gear-beep" which was set to KEEP BEEPING WHILE IN REVERSE. I clicked on this to change it and got the notification I needed to make an in-app purchase which provides a week-long subscription to change any settings I wanted.
IN APP PURCHASE
To process the in-app purchase you'll need to connect to WiFi that has internet access. I got the $9.99 one week subscription. There are choices of many makes, models and years. I just needed the one for my 2017 Prius Prime (and all 2017 Gen 4 Prius). After completing the purchase I reconnected to the TonWon WiFI and repeated the steps to get back to the Reverse-gear-beep setting I wanted to change.
CHANGING SETTING, PART 2
Back at the Reverse-gear-beep setting I tapped on the "KEEP BEEPING WHILE IN REVERSE" which took me to a screen with the 2 available choices. I wanted the other one: BEEP ONCE. I selected BEEP ONCE and then tapped save which took me to the previous screen. I checked to be sure the setting took. To wrap things up power down the car and unplug the TonWon. That's it. It took less 6 minutes including the in-app purchase!
I like the TonWon Pro WiFi because it's inexpensive and works well with OBD Fusion and the Carista apps. I didn't try the app that comes with the TonWon, so I can't comment on that one. The ELM327 WiFi adapter appears to be a common chip set. This one seems as well made as any of them.
Because with the Carista App it got my job done easily I'm giving the TonWon WiFi OBDII 5 well deserved stars. Well Done.
Hope this helps someone