Motorcycle backpack/Bicycle pannier

[SuperFish]

So here's the situation: I'm an avid cyclist (No car) and I'm looking for a bag that fits two seperate functions:

1) Motorcycle backpack: Would like to get something that won't be cumbersome and will hold up at high speed.

2) Bicycle pannier: Looking for something that can attach to my bike and carry stuff with.

I'd like to find something that can hold my helmet, but figure I can create something to do that if need be. Would also like it to be waterproof (but can add a cover if not).

Any suggestions? There's a few panniers that change over into backpacks, but I'm worried about them holding up at motorcycle speeds. I think it'd be easier to find a product that already is a backpack and pannier, but I also am wondering about the viability of adding hooks to backpack (If I find one I really like)to make it into a pannier.

Some of the options from a quick internet search:

Detours Tecco Too - Bicycle specific, good size, can add a waterproof cover later. I wonder about how strong it is. $85
http://www.ebay.com/itm/Detours-Tecco-Too-Panniers-Bag-Backpack-26L-Black-/320664631362?pt=LH_DefaultDomain_0&hash=item4aa919f842

Vaude Cycle 25 - I like the round shape, seems like it would be better at high speeds. Comes with attached water cover. $150
http://www.ebay.com/itm/Vaude-Cycle-25-Pannier-Backpack-Bag-Red-RRP-179-/320883933735?pt=AU_Backpacks_Hydration&hash=item4ab62c4227

Panpack.com Daypack - Like the shape, can't really tell much by lack of photos and internet presence (this doesn't bode well)
http://www.panpack.com/daypack.html

Part of me wonders if I'm wasting my time and should just get panniers and a seperate backpack (but then I still have the issue of wanting to have a pannier I can take with me off a bicycle).

Thoughts?

[scrichton]

I can really recommend the Icon High Viz pack, there is oodles of pockets, a dedicated laptop area and even has tool clips .. plus all to boot it's a high viz vest with true practicality.

Kinda looks like a military vest. Coming from years of being a Lowe Alpine follower for carrying an array of camera gear across the continent, so far it looks like this will go the distance. Also the bit for helmet carries my Shoei Quest quite happiliy into the office, although it has an air of queen bee to the appearance when it's in there.

http://compare.ebay.co.uk/like/300633884868?var=lv&ltyp=AllFixedPriceItemTypes&var=sbar&cbt=y

Failing this a good tank bag, that converts to a rucksack has also been a lifesaver ... mine allows 3 days worth of clothes, an ipad and nikon D3s with a few lenses and charger without even having to pop the expansion section up. I think it was £10 at Lidl So worth every penny spent.

[Formori]

For a dual purpose bag, I would have to go with the Vaude. It won't retain it's rounded shape (since it's not a hardshell) but it doesn't have many straps to flap in the wind, and with the compartments and rain-cover I think it's a good bet.

I use an old Outback daypack for commuting, and the built-in rain fly and ergonomics of the thing make it excellent for everyday use, but the straps on the back have a tendency to dance behind me on the highway.

[iclrag]

I like axio, i think they have a couple confertable things but they make great looking stuff! http://www.axioluggage.com/

[Bluesmudge]

I think it would be cool to rig up a way to mount your bicycle panniers on your motorcycle (as a pannier, not a backpack.)