It's a dream isn't it? To take your recording system wherever you want, wherever inspiration takes you. And where ten years ago you would have filled the trunk of your car with a mixing console, multitrack tape recorder and an effects rack, you can do it all now with just your laptop.
Well actually not just your laptop, you'll need an audio interface too. There are plenty of those around, surely there'll be one that will do the job.
Actually yes, but that doesn't mean there are no practical considerations. Take the MOTU Traveler with FireWire interface. It runs on FireWire bus power so you can run it directly from your laptop.
But – hadn't you better check that your laptop can supply bus power? If it has the larger 6-pin FireWire connector, then it probably can. If it has the smaller 4-pin connector, then it can't. The power pins are the ones that are missed out. You would think that modern laptops would have the 6-pin connector as standard, but they don't all. My recent Sony Vaio doesn't, for example.
And even if you do have a 6-pin FireWire connector, you should wonder whether it can supply enough power. The MOTU Traveler for example draws 9 watts. Now this is no disrespect for the MOTU, but 9 watts is a hefty chunk of power for anything that runs on batteries. A desktop computer can supply up to 60 watts through bus power, if designed to the upper limit of the FireWire specification. But in laptops, available power is not likely to be as much.
To give an example, I have another laptop with bus power. If I plug in a FireWire DVD writer, then the drawer will open and close fine, but it won't actually write the DVD properly. There isn't enough power available.
So, if bus powering current-hungry FireWire devices is important to you, you should check your laptop's specifications closely. Otherwise you might just find that things don't work out as you hoped they would.
By the way, the MOTU traveler can of course run on batteries or an external power supply too, and most laptops will be fine.