Would you use a currency conversion rate tracking website?

While I was building my propane price & vendor tracking website, I thought about tracking currency exchange rates; recent conversation(s) about conversion rates got me thinking about it again.

Would you use a free website (w/ ads -- to help pay for the server, etc.) that...

• tracks the "method" -- e.g.,
  
  
  
  • Visa at Walmart
    
  • ATM withdrawal at Ajijic Bancomer from Wells Fargo checking
    
  • cash-to-cash at InterCam
    
  • transfer from Bank of America to Santander
    
  • etc.
    
  
  
  
• computes the effective rate: e.g.,
  
  
  
  • MXN 1,300 for USD 100.00 is 13.00
    
  • adding a USD 5.00 fee reduces it to 12.38
    
  • (any MXN fee is already "in" the USD paid but not the "amount received")
    
  
  
  
• compares the effective rate against some "representative/benchmark" rate for the transaction's day (or maybe even the previous business day) -- e.g.,
  
  
  
  • One site shows the 7 Oct 2014 "close" as 13.4753
    
    
    
    • (not that there's anything special or "magical" about this site -- it's just one of many)
      
    • (not that there's anything special or "magical" about the "closing" rate -- could use the "open," or average the OHLC, etc. -- as long as it's the same calculation each day)
      
    
    
    
  • 12.38 is 91.88% of 13.4753
    
  
  
  
• averages each of my methods' %ages over time and compares -- e.g.,
  
  
  
  • "Over the last year, my Visa averages 93.2%"
    
  • "Over the last year, my ATM withdrawals average 92.7%"
    
  • "Looks like I should use my Visa instead of ATM cash when I can!"
    
  
  
  
• maybe even compares my methods to others' -- e.g.,
  
  
  
  • "My 'vanilla' Wells Fargo Visa averages 93.2%"
    
  • "I see that other folks' 'super shiny diamond-titanium' Amex averages 95.3%"
    
  • "I should look into getting a 'super shiny diamond-titanium' Amex!"
    
  • (again, the site would store each transaction's effective rate, and not the actual currency amounts!)
    
  
  
  

Like the propane site, it would need frequent use by & input from "enough" folks to be useful & relevant on an on-going basis (not to mention worth building!).

Personally, I wouldn't find much of a need for a site like this.

BUT, how about tracking food prices? For example, prices of whole roasting chickens at WM, Soriana, Tony's, Puritan Poultry, Chapala Mercado, Ajijic Tianguis, Chapala Tianguis. . .or Coffee prices or Tequila prices between liquor stores, or beef prices, or or. . .you could offer these places advertising and they could advertise their specials or new products. . .we could check your site before heading out to go food shopping. . .

You could do restaurants, but I think they'd run you ragged as they open and close so often.

Dunno, just thinking out loud, I know you like to do this.