LibKey Nomad: Browser extension giving one click access to scholarly articles.
QMUL Mobile App: Amongst many other useful functions, the mobile app allows the user to search Library Discovery, and check their library accounts.
Many databases have apps, which allow the user to access material on tablets/iPads:
Arx: Ios app which lets you access arXiv on the go.
arXiv eXplorer: Android app which lets you arXiv on the go.
AMS Remote Access: Allows your device to enter AMS products such as MatSciNet without going through the Queen Mary ezyproxy for 90 days.
Altmetric Bookmarklet: Allows the user to access the latest Altmetric impact statistics for specific journal articles on their browsers.
Endnote: Endnote has both an IOS app and a bookmarklet. The IOS app allow the user to access their references and read their PDF on the go. The bookmarklet allows the user to easily grab references from websites.
Mendeley: Mendeley offers a web importer, which allow the user to easily grab references from online databases, such as Google Scholar and Web of Science.
There are also services, which are based around browser extensions. They can be useful discovering and accessing resources. For example:
Endnote Click: Browser extension which tries to make it easier for the user to search and download documents within their library's subscription, when not available, it tries to source it through Open access.
Open Access Button: Browser extension which enable users to search and download Open access articles.
Unpaywall: Browser extension, which enable the user to search and download Open access articles.