A bike radar alerts you about vehicles behind you. It does not replace a taillight, rather they always (I think?) have taillight integrated. For more details:
replyhttps://www.cyclingweekly.com/group-tests/best-radar-bike-li...
Radars don't save you nor do they tell you which motorist will run you over and which will not. So it doesn't help you take decisions on wether to take evasive actions such as jumping in the field next to the road.
replyRadars don't push cars away from cyclists.
They are more a placebo than anything really.