Is this the future of mudguards? Five cool things coming soon from Ass Savers, Specialized, Prime, Magene and Bell

I got the 530 as it was about 38% off. I couldn't justify the other models.

OK, during an activity you should be able to press Enter (top right) and select Light Network. 
https://support.garmin.com/en-GB/?faq=H428bBYMVA3tX87Q40OE37

Thanks but unfortunately it says

Edge 520 Series | 530

Well, it's expensive considering it's within a fiver of the current price of the established brand leader. I'd expect it to seriously undercut the Garmin equivalent - for just a fiver extra I'd play it safe and go for the one with a proven track record.
Edit - mind you, USB-C charge port might swing it for me!

Its a different use case.

Radar is general awareness.  Particularly useful for "Car Back" in a group and advance decisions about Road position (eg Secondary vs Primary).  Its got considerably more range than your ears.

Camera is close pass support and reporting.

hawkinspeter wrote:

That rear light is expensive considering it doesn't have a camera. I don't see the point of radar without a camera - what are you going to do, bunny-hop over a car driving behind you?

Arguably the opposite is true - a camera does nothing to help prevent a collision or close pass; all it does is record it so you have evidence after-the-fact. Radar on the other hand might* help inform your positioning etc. in order to actually stop an incident occuring.

* I don't actually have a radar device, so this is just theoretical for me. 

The only use case I've seen presented that I agree is of value, it let's you know theres something there before you make a change of position on the road, however a shoulder check would be just as effective. The only time I'm generally shocked by something passing is other riders, but no ones ever said these can pick up other bikes and equally if people stopped trying to grab max aero benefit from you as they passed.

It will pick up other riders(s) if their speed is slightly different from yours - not if they're on your wheel and staying there. I believe it uses Doppler Effect and is triggered by closing objects, rather than big objects. I don't know what the threshold is, but mine goes off if the bike is parked and I walk up to it. 

OnYerBike wrote:

Arguably the opposite is true - a camera does nothing to help prevent a collision or close pass; all it does is record it so you have evidence after-the-fact. Radar on the other hand might* help inform your positioning etc. in order to actually stop an incident occuring.

* I don't actually have a radar device, so this is just theoretical for me. 

Yeah, I'm just sceptical that there's much you can do when a vehicle is coming up behind you. However, I use a handlebar mirror which can perform a similar function although it's mostly used for having a quick check for gaps in traffic for when I want to perform a maneouvre.

I still think a rear camera would be ahead of a rear radar in terms of usefulness.

It reckons to detect approach speed differentials of 6-99 mph, but as mark1a says, it will go off walking up to it, so I think it's more sensitive than that, probably around 4mph. Certainly it's picked up faster cyclists approaching.

I'd say it's of most use on country roads with light traffic, but still useful in town if you're not on a main road.

I also have a mirror and the radar means I don't have to keep checking it. I only need to look in the mirror when the radar goes off, then I can start planning what to do depending on the vehicle approaching.

I find it makes rides a lot more relaxed, as I'm not constantly looking and listening for what might be coming up behind me.

HoarseMann wrote:

I find it makes rides a lot more relaxed, as I'm not constantly looking and listening for what might be coming up behind

Absolutely that, plus it's able to detect the vehicle beyond the range of hearing so gives more time for a decision without stress.

This is getting worse with EVs more common as tyre noise alone isn't enough to overcome wind noise above a slow ride pace.

lonpfrb wrote:

HoarseMann wrote:

I find it makes rides a lot more relaxed, as I'm not constantly looking and listening for what might be coming up behind

Absolutely that, plus it's able to detect the vehicle beyond the range of hearing so gives more time for a decision without stress.

This is getting worse with EVs more common as tyre noise alone isn't enough to overcome wind noise above a slow ride pace.

My friend uses one and it's audible enough that when I am leading I can still know vehicles are approaching, and if I am behind the increase of the light flashing is good visual signal for awareness.