Google Checkout has enabled mobile payments using WAP. Now any retailers in the UK or US that accept Checkout and have WAP enabed sites can accept payments from customers from mobile phones.
PayPal have supported payments via mobile phone (cell phone for those in the US ;-)) for some time. However their offering is more appealing for many applications as it works via SMS text messages. With PayPal you don’t need to be browsing a WAP enabled website to make a payment, you simply text the amount you wish to pay to the phone number of the recipient. PayPal already had a WAP interface when they introduced their text message payment service.
It’s good to see Checkout adding more sophisticated services, but they’re still very much playing a game of catchup.