1. Silk LinerPerfect for when you're on a sleeper train or sleeper bus. In Vietnam there was someone in our bed before we joined the train, so the linen wasn't fresh. Another benefit is when all you're given is a duvet and it's just too damn hot OR only given a blanket but the air con makes it freezing. A little silk layer makes it. Because the liner is sealed like a sleeping bag (though my design is much more spacious) you can put your valuables at the bottom while you sleep, stopping opportunistic theft. Cotton and microfibres options are available, but may be more bulky or not as cooling.
Jag Bags Pure Silk Liners come thorough it recommended and come in a variety of shapes and colours including the awesome tie dyed.
2. PadlockI was surprised to find how many travelers don't have a padlock. I use it not only for lockers, but also for my baggage on transport or when there isn't a locker available. There is the argument that doing this draws attention to your bag and indicates that it contains something worth locking/something worth stealing. While I do believe there is a case for this (a friend was a victim of this targeted theft and had her bag slashed a few years back in Tenerife - hers was the only bag with a padlock) generally theft, particularly in Asia, is opportunistic. When choosing a padlock, pick a combination padlock as keys can be easily picked. I liked the flexible wire padlock for my bag and it helps with awkward shaped lockers. Having said this I would take a metal padlock too - they're only small and always worth having to hand.
Pacsafe do TSA approved padlocks meaning airport security can safely access your bag for security checks if needed, without breaking the padlock. They do many other gadgets to keep you safe while you travel and are worth a look.
3. Backup phone/USB chargerMy Uncle bought me a Mophie Juice Pack as a present and it's been endlessly useful. For minimal extra space and weight I have double the battery. I've used it when bus journeys are long or when I don't want to leave my phone charging unattended. I use it only when necessary, so should anything happen, I still have that extra battery to phone a friend and yelp "HELP" down the phone.
I have the Mophie Juice Air for 100% extra battery, but there are chargers the size of the iPhone which you plug any USB charger in to which offer even more battery for a greater variety of devices.
4. Dry BagI bought little 'plastic wallet type' zip up bags for my kindle, phone and money/tickets. Though ok, they broke pretty quickly and looking back I would have just bought a dry bag straight away. Although a big diving dry bag is more bulky, it's more effective and acts as a big (and infinitely cool) beach bag which you can take in the sea, down rivers, pool parties, tubing etc. There are many dry bag options out there including ones just for your phone or ones that are duffle, bum bag or backpack shaped. If buying one in a shop, check if they come with a guarantee and check their effectiveness in salt water (the same applies for waterproof cameras)! Surfing and dive shops and some hiking shops are good places to look, but the internet will give you the most options.
Over Board sell a variety of waterproof bags and many of the options I mentioned above. The one pictured is very similar to mine and I found the 5L size a good size for my valuables, but you need to make that judgement.
5. MoneybeltIf a bag is on show it's a target. Although a majority of the time I carry a bag there are times when "out of sight and out of [their] mind" applies. I often take my money belts in cramped places and at night just for added security and reassurance. Carry only what you need so it doesn't bulge leaving your phone and cameras locked at your hostel. Reach in to your money belt as little as possible so as not to draw attention to it. Added precautions never hurt and this particular one combats against bag snatching.
This neat little money belt is from Gap Year Travel Store and is waterproof! You can just get simple little ones from places like Tesco and boots.
Are there any other gadgets that would have made my life infinitely easier?
All images taken from supplier website which are linked to beneath image.