Tracking your performance, always important when you want to train more efficient, but also much fun to revisit old tracks when rehashing past kayak trips. The possibilities to track your activity are almost endless.
Before I bought the Polar Vantage M, I used my smartphone in combination with runkeeper. I switched to strava because there you can choose a kajak activity and runkeeper just calls it rowing. A small but important nuance in my humble opinion. 
What kind of app you use isn't important, if you want to change between them without losing your history there is always https://tapiriik.com/ A very useful, free synchronizing tool between all kind of different activity trackers.
Now, in short, about the Vantage M, it is a wonderful peace of equipment. Great value for money, some people may find it expensive but considering how well it works, I find it a great buy. Easy to use, long battery life during tracking, great accuracy. The Polar flow app works great, although i rather use strava to view my tracks, but thats a personal preference. The two apps are synchronized so it doesn't matter which one you prefer. 
The watch is being heavily supported by polar with regular updates and it's a nice looking watch. The glas is very sturdy, even after six months of heavy use there isn't a scratch on it. I never take it of, so it has seen a lot of water, be it hot or cold, dust, mud and even birdshit and paint. I keep it on during construction work, gardening, etc. The only remark I have is that the black strap isn't completely black anymore. But considering the kind of use, the watchs gets a big 9 out of ten from me.

Some pictures have been made with the S32 and 33 Nikon,  a relaible rugged point and shoot camera. It doesn't float so beware, I have tested it against my will and lost one! Still dreaming of a nice rugged full frame compact system camera naturally.
Until  then my trusty Nikon D7200 with 18-300mm 3.5-6.3G Nikon lens is a worthy alternative. A good zoomlens is a nice thing to have when shooting wildlife pictures. When things get darker i use an inexpensive  but good value for money 35mm1.8G primeNikon lens. My main problem on camping trips is that many times i just don't have enough room in the kayak to take it with me.

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Not enough room in your kayak? SOLUTION: The overboard on deck dry bag. A very easy to use drybag, with some bungee cord on top to replace the one you lose when you cover them with the bag. It stays dry even in the worst conditions. It takes some time to get your camera but you know he is safe and with 20 liters there is room for a towel, my binoculars and some snacks. Great value for money.

A cheap but good manual pump is all you need to empty your boat after a bit of self rescue.

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A cheap but sturdy peddelleash can also be used to hold the boat at bay while you galanter on the shore. 

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A good spray deck comes in handy in the wintertime. It keeps you and the inside of your boat warm and dry. 
Also useful when circumstances are not so sunny and dry. Keep in mind that waves are strong, so you need a tighter fit at sea, like the one on the left. when not at sea, I use the one on the right because it's easier to close and open.
In summertime you can use a half spraydeck, keeping your cockpit dry and yourself a lot less sweaty.

With a kayak full of gear you will be very thankful for a good set of wheels, even the cheapest carts will be able to do the job. Keep in mind that smaller wheels get stuck easier then bigger ones.
You will need a strap to secure the kayak to the cart. There are models who are fully collapsable but they are expensive. Most carts have detachable wheels so you can store it in your kayak, on camping trips I usually have to strap it on the boat instead. However it is the first thing I leave behind when I turns into we. Mostly because it takes up a lot of space compared to just carrying the boats. When your boat is fully loaded the standard handles may not suffice and can be a bit painfull while carrying. In that case you can use some kind of straps like the ones on the right.