Just finished installing front parking sensors. I tried some cheapies from eBay and they just didn't work properly for this car. So I ordered a more expensive one and it works great. You don't want those sensors on full time, so there is usually a mechanism for turning them on and off. The factory installed ones use a speed sensitive switch to turn them on and off. That's difficult to do aftermarket. The one I purchased as activated by the brake switch and set by the back-up lights. The weakness with that setup is that if you step on your brakes at speed, the unit could go off depending on the type of road you are on and whether it is raining or not. So instead of the brake switch, I installed a momentary switch. The unit stays on for either 5 or 20 seconds, so you don't need an on-off switch. I've set mine for 20 seconds. For the back-up light, I installed an on-off switch since it only needs to be activated for occasionally setting the unit.
There is a place in the corners of the grille to install 2 sensors. From my experience, you don't need 4 front sensors and this unit can handle two sensors. The placement of these sensors in the grille is hidden so you really don't notice them. The sensors come with a 4 degree frame which points the unit up 4 degrees. There are other frames included, 0 and 10 degrees, but the 4 degree frame works best. Because our car is low and the sensors are thus lower than recommended, you need the frame to point the sensors slightly upward. I installed the momentary switch just to the right of the trunk switch, and it looks built-in. I installed the on-off setting switch below that underneath the dash so it is out of the way but still reachable. Be careful to install it precisely where you have room in back. I removed the lower dash panel by removing the end cap and two screws, one under the end cap and one just below the dash on the right. It just pulls out from there. The display unit was installed on top of the rear view mirror and fit there perfectly.
Below you will find the links to the unit and switches as well as pictures.
https://www.sonicelectronix.com/item...18.MATT.2.html
https://www.amazon.com/gp/product/B01KA4FM4Y
https://www.amazon.com/gp/product/B01G821G6A