I'm not quite sure why you are stating helmet shortfalls in this thread when there is a specific thread for it here:The mate broke his wrist and those things aren't intended for multivehicle collisions
Not sure why they state the number of cyclist casualties but not casualties of other road user types.Casualties by road user type
In 2017, the highest number of fatalities were car users, both drivers and passengers, who accounted for 44% of road deaths (669) in the UK. 
There were 470 pedestrian deaths in the UK in 2017, a 5% increase on 2016. 26% of all road deaths were pedestrians .
There were 101 cyclist deaths in the UK in 2017, a 1% reduction on 2016. There was also 18,321 cyclist casualties on Britain's roads in 2017, a 1% decrease on 2017. However, between 2016 and 2017 there was a 5% decrease in cycling traffic on 2016. 
There were 349 motorcyclist fatalities in 2017, up 9% from 319 in 2016. Compared to car users, motorcyclists are 55 times more likely to be killed, and 81 times more likely to be killed or seriously injured on the roads in Britain. 
Going back to the question that the OP asked rather than other questions. The OP's other half might be reassured by the OP deciding to wear a reflective and / or helmet. Another anxiety easing measure might be to use Strava and the beacon feature so that the OPs partner can see where the OP is on his ride.There's almost no evidence for the first bit in the real world (dazzle camo is still camo), repeating such myths discourages cycling and the last bit is a much bigger problem. Please don't exploit this collision to push them.
Then someone should suggest how to explain the reality to the OP's wife rather than encourage the OP to possibly increase cycling risks in order to fit in with mistaken views. There are enough people with odd beliefs about cycling out there to be unhelpful (calling for bad laws, refusing to convict incompetent motorists when on juries and so on) without cyclists letting our families be among them.Going back to the question that the OP asked rather than other questions. The OP's other half might be reassured by the OP deciding to wear a reflective and / or helmet.
Yes. Any remote-requestable tracker will do that. I think they're good ideas generally but not the snoopy commercial ones. Even a simple "find my phone" app will often work for this.Another anxiety easing measure might be to use Strava and the beacon feature so that the OPs partner can see where the OP is on his ride.
Another great idea. https://bikedata.cyclestreets.netIt could also be worth using something like cyclestreets to look at the number of incidents (unless your route is fraught with peril!) that occur on the route to illustrate that actually, this was a real one off...
bang on, at this big roundabout I got into it first and had a bright flashing day light on my bike and another on my helmet, I looked that taxi driver in the eye and then did my hand signal, the flashing lights and signal got his attention and he slowed and waited for me to pass. But my mate was just a few metres behind and apparently was in his A pillar and therefore got hit, regardless, the taxi driver was at fault 100%.I have been hit by a car exiting a side road because I was obscured by the drivers A column. They are so thick on modern cars that they are a danger to smaller road users. You have to look the driver in the eye. Only once has a driver looked me in the eye and accelerated towards me.