Content is king! Just ask anyone who is serious about the web and they will tell you, unless they're in the midst of getting you to sign away your content at the moment. As a consultant or other person on the go, you should be ready to capture content at a moment's notice. Now, I do a ton of community work, so I probably take this to extremes, but you should consider these options.
A picture is worth a thousand words, but a video is king. Be it user groups, scrums, product demos or anything else having a video camera close at hand can solve a ton of problems. I carry a nice cheap video camera in my backpack which I picked up during a Black Friday sale. My unit is a Panasonic PV-GS85, which has a great built in LED light which can help with close up camera work in dark rooms. The model is not important, they key here is that having some sort of video capture really helps. There are three levels of video cameras these days. Flash, Tape, and Hard Disk.
Mine is a tape unit, that records to Mini-DV. This means I can record a lot, about 1.5 hours per tape, but it means I've got to rip the tape back to digital files at 1:1 speed when I'm done, which means 1.5 hours of recording is 1.5 hours of ripping.
Flash units store less, but also store as digital files so they transfer to a computer much faster. These can also be very small sometimes, which is nice. They can also be cheaper than tape.
Hard disk units are more expensive, and about the same size as tape units but they also transfer to your computer faster because, again, they are storing files to that hard disk.
On all of these, when you get a unit realize you're not trying to film a movie, O.K. quality will likely be fine. Good enough, is by definition, good enough.
Video cameras are great, but shaky video isn't. I carry a mono pod in my backpack that I can whip out whenever I need to stabilize a video. These gizmos are handy, but remember that mono means 1, that's 1 leg, which means no walking away. For walking away you'll need...
I bought a "large" tripod at my local camera shop. It stays in the car, to big for the backpack, but it is still relatively nearby if I need to record a longer session. Usually I know this on my way in and will carry it with me. I've made a habit of recording our company meetings for Sogeti so that they can be shared on our SharePoint portal. This has worked great for me.
But sometimes you want to walk away, and haven't got time to get the large tripod. For this, we use the wonderful QSX 1001 tripod. This tripod packs up into a 2 inch diameter, 7 inch long tube. It rides in the water bottle pocket of my backpack, and is always ready to be pulled out. Now, even fully extended this only rises to a height of about 12 inches, but resting on a table this is perfect for interviews.
Sometimes the full camera isn't what you need, instead its time to participate in a Live Meeting session or other Webcast and you just need a web camera. I carry a Microsoft LifeCam NX-6000 for this. I'm a fan of this unit, but it's drivers are enough to drive me crazy. The drivers install a service (MSCAMSVC.exe) which can start consuming tons of CPU cycles even when the camera is disconnected. I now keep the service disabled until I plug in the camera. What I really need is a better Web Cam at some point that lacks these problems. This unit is workable, just realize you're going to have to seize control of that service of your box will seriously suffer.
Audio Capture & Playback
Sometimes you don't need video, and audio alone will be plenty. Sometimes you just want to listen to some tunes while you're cruising along to your code. Here are my tools for this.
We all need tunes, and we want them on the go. While I own Zunes and iPods, as Alton Brown says, I hate unitaskers. The Creative Zen V Plus, I've used for years and remains the staple generic MP3 player in my work backpack because it not only plays WMAs, MP3s, and Audible audiobooks, it also has a built in recorder. Now, this isn't super high quality audio, but if you've got a morning Scrum that you need to record, or if you need to write yourself a verbal note, then this is the unit for you.
If podcasting is your goal, then the Zen V Plus won't be up to the quality you want. You need a good quality recorder which can capture audio in multiple different ways. For my purposes, this is the Zoom H4. This unit can record with its two built in microphones, it can accept two direct inputs from guitars or other instruments, or it can take two XLR microphones and provide them up to 48V of phantom power. Best of all, it just plugs into your computer for retrieval of the information, and stores to common SD memory sticks. It also comes with its wall socket adapter, or can run portably with 2 AA batteries. I use this for my podcasting efforts, and have been very happy with it so far.
When you're done capturing, you're gonna want to listen to all that wonderful content. I've raved in the past about the Logitech Freepulse headphones, and I'd still recommend them. The customer power scheme still bothers me though.
There are more than cameras to image capture...
No cameras are in my backpack, at the current time the camera in my phone has always been enough for what I've needed. When I vacation I might add my wife's camera, but otherwise camera phones are the key here.
The technology most locking down the modern mobile office is fax. There are a bunch of service options for this, but those services don't also help with the problem of being handed a piece of paper that you want digitized into OneNote or other computer note taking software. For this, I carry the Pentax DS Mobile 600 which is a wonderful, USB powered, color scanner. This unit will rip through your pages of hand written notes and digitize them for your digital consumption. Fair warning, at the current time there are only 32 bit drivers for this unit.