Payments and Billing Expertise
One of my goals has been to build a knowledge throughout the payments and billing space, and not focus a single vertical.  The rationale is different payment verticals have varying degrees of integration, and it would prove useful to have hands-on experience across multiple industries.

Mobile wallets, for example, touch upon card schemes, stored value, and banks.  Bank payment systems, on the other hand interact with Real Time Gross Settlement Systems (RTGS), Clearinghouse, and SWIFT payment systems.  Electronic Bill Presentment and Payment (EBPP) and Electronic Invoice Presentment and Payment (EIPP)  integrate service consumers and providers for the purpose of accelerating order-to-cash.  Even Bitcoin needs a rail to load funds into the system, whereas blockchain promises to integrate reconciliation into the transaction and thus potentially disrupt some industry verticals.

A key underlying component to all payment systems is settlement, which includes complex fee splitting, reconciliation, and disbursement.  This component is complex due to round-trip audit requirements, and is a key skill which weaves throughout my many payment experiences.
Mobile Wallets
Issuer & Acquirer
Stored Value
My role as Enterprise Architect for Samsung Pay has put me in a key position to understand the most recent mobile wallet best practices.  My focus on settlement-related processes allows me to play a key role in the money flows behind the mobile wallet concept.
The payment card industry provides unique perspectives for Issuers, Acquirers, and Merchants.  My roles at both mobile wallet and stored value firms have given me unique insight to these perspectives.  Further, my relationships at the Saudi Arabian Monetary Agency has given me insight to the card scheme perspective via the Saudi Payment Network (SPAN)
My role as the CIO of a stored value firm has given me significant experience with how to apply this concept to payroll cards, government benefits (e.g. food stamps, unemployment, etc.), general spend, rewards, and more
EBPP / B2C
Settlement
EIPP / B2B
Settlement is a key underlying thread spanning all my payment experiences.  Some of the more complex have been with the mobile wallet and stored value, as the complex fee splitting to support all parties facilitating transactions can be difficult.
The EBPP system I built for the Saudi Arabian Monetary Agency provided a centralized hub for most major post-paid billers in that country, and allowed consumers to view/pay these bills from their bank channels.  The system is used at customes, to ensure anyone leaving the country has paid their bills, and has also been expanded to provide an eCommerce component.
I have architected and implemented an EIPP system which has been deployed at Office Depot, Dell, and other locations, so have a firm grasp of the order-to-cash processes.  Billing and payment are key aspects this industry vertical.
RTGS / Clearinghouse
Card Schemes
Blockchain
A card scheme is both a technical and legal framework for conducting consumer payments at both point of sale and eCommerce.  I have worked with the major US credit card schemes, and have indirect expereinces with central bank card schemes such as Saudi Payment Network (SPAN).  My work has also encompassed private label and debit card schemes.
I am actively working in an advisory role for applying HyperLedger to both financial and non-financial business solutions.  My expertise is with product definition, architecture, and chaincode development.
The Sadad Payment System which I built for the Saudi Arabian Monetary Agency has a direct integration with that central bank's RTGS.  In addition, my work within the banking industry, stored value firms, mobile wallets, and more, has given me a number of experiences in working with both RTGS and Clearninghouses.
Banking
Payments Hub
SWIFT
I have played the role of an Enterprise Architect for a large international bank which was undergoing a major transformation initiative.  As such, my experiences touched on systems spanning most aspects of the banking industry.  I have also performed many bank integrations from private entities.
I have introduced the Payments Services Hub (PSH) at both banks and private entities as a means of centralizing payment initiation, repair, and related processes.  The idea has been to re-orient organizations to see payments as a profit center, not a cost of doing business.
SWIFT is an important network supporting international payments.  My work at both central banks and international banks has given me unique insight and experiences with this network.