This is something I've been thinking about for awhile. I believe it really depends on the situation.
For example:
1. coin/relic hunting around town
2. Remote areas, day only
3. Camping/overnight/hiking etc
For general detecting, a daypack and a typical detector bag should be fine. I'm not sure how useful it would be to strap the detector to or carry it in a backpack. Vehicle shouldn't be that far away, right? Altough where I live, vehicle break ins are very common. If you leave anything visible in your car at a beach, trailhead, or around town, it will get broken into sooner or later. So I could see not wanting to leave anything in the car at all.
If you have a Deus, like others said the answer is XP's 280 backpack. It's made exactly for that. I don't have a Deus, but I've considered getting the bag. If you want an all in one bag that doesn't require breaking the detector down completely, like Pete said a tactical rifle bag should work. You'd just need to get one long enough. I think they're probably the way to go if you bring a second detector. Garrett's camo bag is probably not much different than one.
For something out in the sticks, like say nugget detecting and maybe some gold panning, a 5 gallon and a pack of some sort is probably the way to go. I'm considering attaching a 5 gallon to an external pack frame that has a shelf. Would be useful for rockhounding or hauling trash as well. Probably a matter of whether you want your hands free or how much other stuff you'll be bringing back. Ideally, you'd have someone else haul it!
For anything that requires camping, a large ruck with the detector broken down inside it, and a smaller packable pack. In this situation, you'd establish a campsite then use the small pack for the general area etc When I was in the Army that's basically how we'd do it.
Would love to hear other's thoughts on these.
