Hi,
I can do it.
I am working with Verifone Vx510, Vx520 and Vx670.
I can show you demo video and I am understanding your project.
You want from Vx510 device call your webservice then execution some transaction: book, payment, topup, loyalty....
Please send me more detail info.
Let me know your skype id, we will discuss more detail.
I can sign key for each application on device with 10$ each program
Regards,
--Hung