Great question and this is something we struggled a lot with internally as a lot of our processes and applications are legacy. Upgrading / replacing them takes a while and we still need to deliver quick wins to the business.
One product that worked well for us was Capriza. Capriza delivered mobile-first approvals for several of our legacy applications and enabled our executives and managers to get work done, even while on the go. The platform only works on web applications (last I checked) and even then, doesn't work on every web app (struggles with modern web apps).
Capriza uses web scraping to translate complex actions on the desktop to simple actions on a mobile device, natively. We enabled approvals from Salesforce, Oracle, and SAP, all in one native app that our users can use anywhere to move approvals forward quickly. From demo >> first app deployed took us ~6 weeks and we felt pretty good about the result. We've added more approvals since, but haven't taken advantage of non-approval use-cases as yet.