Lots of things have improved in the last 5 or so years with regards to hosting.. faster hardware, improved control panels, cheaper bandwidth.. but the ability to keep your eye on your box whilst out and about is definitely amongst them I'd say.
So share your tech tips for when you're not at your desktop for monitoring your sites.
Key hardware: My iPhone. 3G is prevalent in my locality, but the deal on o2 means I also get free access to the two largest UK public wifi hotspots - TheCloud and BT OpenZone. Whilst some of these are free anyway (such as ones in pubs) being able to walk through town whilst on a wifi connection can be really useful if the 3G is lagging or just not there.
Pingdom - It's not the flashiest of all apps, but it tells you what you need to know - is the server up?! It'll echo all your reports for all servers into one quick and easy screen. I really hope Pingdom puts even more time and effort into this, it could make the service unbeatable with a few more features. The app is free too, which is a bonus.
TouchTerm - there's a bunch of SSH clients for the iPhone out there, I've not had chance to try any of the others but will do at some point. All my accounts are bookmarked in and I can replicate whatever I need to with ease. I've installed software and configured it with relative ease just using the touch keypad. It was either free or at most a dollar or two.
iStat - The software/server combination used to be Mac only but someone has ported the server side over to *nix now and it runs pretty well. I'm having issues with one of my boxes showing it's bandwidth usage but I'll look more into that. Live CPU/Memory figures AND graphing?! Very impressive, and if you're doing face to face with your client it's bound to be a good thing to show off (make sure it's working first tho!!). It was £1.19/$1.99 on promotion when I bought it, should still be for a little more.
Critical email accounts IMAP'd - all my key accounts are on 15minute checks, and I'll be making an emergency PUSH account for when time is very much of the essence. Having instant access to email is absolutely essential on a handheld device these days, and the iPhone does a pretty neat job of it.
EverNote - great note syncing between various boxes. No more having to ring people to jump on my laptop to read me out an IP address or similar ever again.
So what do you guys use when you're out and about?