Informer is described as 'provides key information about your IPhone/IPad device, including disk and network information, user environment, RAM and other details' and is an app in the OS & Utilities category. There are nine alternatives to Informer for Mac and iPhone. The best alternative is iStat Menus. It's not free, so if you're looking for a free alternative, you could try Stats or eul. Other great apps like Informer are Stats Panel (Free), RunCat (Free), Translucent (Paid) and Beaconly (Free).
iStat is a series of system monitor apps. It's available in different versions: iStat Menus, iStat for iOS and iStat Server as a companion application to the iStat for iOS app that lets you remotely monitor your computers (free for Windows and Mac).
Beaconly is a flexible, easy to use data aggregating menu app that ties relevant information to you, beautifully one click-away in your macOs menu bar. Easily discover status of AWS, your Jira Tickets, and so much more.