It is very easy to expose your adf code in any application module as services with just a couple of clicks.
(Although this may not be the best thing to do without thought)
This could allow you to leverage your existing investment in ADF and publish the existing code
as needed to your SOA enviroment.
You can base Entity Objects on services and have all the same rich functionaltiy adf provides yet using a service backed entity.
Webservice data control
This control allows you to incorporate web services in any ADF page simply and quickly
Pojo custom control
This allows you the most flexibility you can create a custom data control off a pojo and use this to call you web services.
With these tools you can integrate any third party or internal services into your adf application quickly and easily.
All in all I was pleasantly surprised with the service integration in ADF.
Although there are a couple of things that where tricky (custom LOV's etc) you should be able to achieve
what you need with the minimum of fuss.