For UK paddlers - the RYA SafeTRX app

I've only just heard about this. It is an app where you register yourself, emergency contacts and craft.

When heading out, you create a planned route (departure point, arrival point and waypoints) plus departure/ETA.

If you don't check in by the ETA, it sends alerts to your emergency contacts. The alerts include the number of the nearest Coastguard.
Better than that, your route is saved on servers that the Coastguard can access, so they can immediately see where you were planning on going. 

The RYA Safetrx site has a certificate problem so I can't link to that. 
The app is available for Android and Apple.

Yep, here in South Africa, it's the "NSRI SafeTrx" app, same functionality, but the back end is integrated into our National Sea Rescue Institute's systems.

Many South African paddlers use it as a matter of course and it's already saved at least one paddler's life.

• Saved by SafeTRX
• Using SafeTRX AND a VHF Radio in extreme conditions 

It's important to recognise though that SafeTRX does have multiple potential points of failure whether it's the risk of your phone battery failing or the connection to the mobile networks - and this is why, especially in extreme conditions, I always carry, in addition to my phone/SafeTRX, my VHF, pencil flares and whistle.  (Don't underrate the whistle!)

I've since been told that it is in standard use in surfski races in the UK - seems that this info hasn't reached the wider paddling community. 

The focus is on offshore, but I think its use could be very applicable to winter paddling. From my club there are a number of people who train alone in winter; the river is placid (well, it is a muddy, duck-pooh'd ditch), but in winter it is very cold. A capsize from a racing boat and cramp can put someone in serious trouble, even if they make it to the bank. So using the automatic alert function would be useful.

I've ordered a whistle and compass, although other boaters, even fishermen, are a bit sparse around here. VHF reception from a kayak or waterlevel is unlikely. Oddly enough, there is more chance of picking up a mobile signal, since there are quite a few towers on headlands.

VHF reception from a kayak or waterlevel is unlikely. Oddly enough, there is more chance of picking up a mobile signal, since there are quite a few towers on headlands.

Correct.  There are two factors that come into play for us here in Cape Town with VHF, however:

• False Bay (where I do 99% of my downwind paddling) is surrounded by mountains, and there are VHF repeaters that ensure line of sight - so we have surprisingly good results talking to Cape Town Radio, who monitor the emergency channel 16.
• I have personal experience of having to guide the rescue craft to our position using the VHF.  They had our approximate position on SafeTRX, but couldn't see us.  Depending how you've set SafeTRX to update (you can configure the update interval to 10min, for example, to save battery), you may have drifted some distance from the position that they have.  More often than not, the guys on the surfskis can see the rescue vessel long before they can see us - and the VHF is great to be able to talk them into the actual location.