WorldFirst does. There are plenty of competitors in the space that do a great job at this.
The two turned out to be nothing alike. Oanda used to let little people convert currency on the same platform as proper FX traders (speculators). This meant you could pay a tiny fee and get some of the most competitive rates in the world because you were trading directly in their two-sided market.
WorldFirst is different. They make you declare the amount you want to exchange and then they synthesize a rate that expires soon after. There is no way to put in an order at a specific price and they do not show you a two-sided quote which would make it plain how much they're taking.
From what I saw, WorldFirst aims to take about 1.5% of each side of each trade at the when they are large, and even more on small trades.
If you're exchanging $500 you may as well use a bank. If you're exchanging $50000 you may as well use a true trading platform.
When exchanging currency at any online or physical marketplace, look at their two-sided quote to see the spread they charge. If they try to show you only one side (buy or sell but not both), go elsewhere.
On average I send between 500-1000 GBP to USD per month on Transferwise and pay 2.50 - 5 GBP in fees. Compared to a wire at a bank that charges 30 GBP fixed + a % on a sliding scale depending on the amount, it's not really competitive until you get over 10k per transaction. But then at that point you can contact TransferWise customer service to negotiate a better rate.
Thanks
For larger transfers (ie above £5k/$6k) you have a slew of them; Global Reach Partners, Moneycorp, World First, and Rational FX to name a few.
Disclaimer: I am a co-founder of CurrencyTransfer.com, an aggregator of some of the above larger transfer companies.