A few I can recommend that I use myself are Mortgage Calculator, Zillow, and Sign Easy.
All offer different tools to help make the job easier. The two are self explanatory and Zillow deals with home listings.
Zillow is the only one I use myself. Most of my work is done on my office computer using software, not apps. Nothing wrong with doing it that way though I am sure it is way easier but I have a system that works for me so I stick to it.
MLSIMPORT
Although it’s not a dedicated mobile application, MLS Import can help your business and saves you a lot of time and money when creating your real estate website. MLS Import is a RESO API based import tool that allows you to connect to your MLS and showcase MLS properties from your area into specific Premium Real Estate WordPress themes.
MLS Import is a new popular plugin that thousands of real estate agents already use to build their Real Estate website. Contact their support team to confirm if your MLS is on the supported list, and MLS Import staff does all the work for you!
PlanOmatic, Matterport, and Hutch
Virtual staging has never been easier for real estate agents and brokers. Agents, communicating with potential buyers across the country, can create accurate, shareable, and interactive floor plans for their listings. PlanOmatic, a team of photographers who create true-to-life floor plans for clients, Matterport, the software behind 3D virtual walkthroughs, and Hutch, a home staging software with furniture you can buy, all bring what was once science fiction to life for agents and clients.
Bigger Pockets is a nice app for those getting started and wanting to learn.
Xome is nice if you're looking to buy. You can snap up some great deals from the auctions on there.