Accounting and Project Management Integration

General information for the business: Translation Services
Description of requirements/functionality: We need an integration between our project management system (API docs available) and Xero our accounting system. Xero has an open API with all details available on line. Development can take place in sandbox environment.

We need:
Client and supplier details synced with Xero (ie address, contacts and bank details)
Supplier bills and invoices generated in PM system synched with Xero
Once bills and client invoices are paid we need the status of the bills and invoices in the PM system to be updated.

We need someone who can manage the whole integration with experience in using APIs.
Specific technologies required: java, php, API
OS requirements: Windows, Other
Extra notes: The integration would need to be built with future development in mind. PM system API docs can be sent to interested parties. The PM system is on a Windows server and the integration be hosted on this. PM system is called Plunet (www.plunet.com)