I agree with the benefits you describe; I used to work for a supermarket who released a new points card. I had to attend endless presentations about this card. The result was that the supermarket would experiance greater customer loyalty and, most importantly, gain customer information. Many buisnesses would adopt your scheme if it providd accurate customer demographic information and stuff like average sales, etc.
Yeah, your argument for installation is a good one. If somebody paid me to do this, I'd buy the cheapest WRT54G I could
find (£60), I'd then flash it with the Sveasoft
firmware and install it. The sveasoft stuff does everything you've mentioned. If it doesn't it wouldn't be hard to implement with a little imagination. I'd also do a short site survey and recomend any antenna upgrades, multiple access points, etc. Of course, I'd recomend multiple access times much of the time. This is not just because I'd recieve extra money, but because, I think this is a better idea than omnis. Anyway, I'm drifting off-topic.
This whole process would take very little time to do. I'd charge £200 - £250 (about $500) for the hardware and installation. Obviously, this would rise with the addition of more hardware and they'd have to pay for a tank of petrol. Selling a single access point would give me roughly £190 profit for a days work, if that.
I'd remove the monthly fees by installing a web based interface on the box. I can'd find the URL, but, you can get some good stats of those WRT54Gs. The owners could look at these for free and at their lesuire. If the owner wanted, I could make this visible to the wider internet and set them up a domain name for it, something like
www.coffeeshopstats.com. This would be password protected and would cost extra. Probably, £100 or there abouts. I'd email clients about (selected) available updates and charge £25 a time to update their box. I'd do this via ssh and wouldn't have to leave my house.
Obviously, they have to advertise all this, something my scheme fails to do.
And yeah, I'm a student and therefore have a strange perception of money. I would not do this as a job, either, so profit margins don't mean that much to me. I'd just like an easy way to earn £200 in an afternoon between lectures.