The Gaming Den

Things like virtual tabletops, something that could reveal a map as people explore it.

Roll20 is usable on mobile devices with a paid subscription. I really like Roll20 on PC, but I don't have a subscription, so I can't say for sure if it's any good on a phone.

If you just have your browser get the desktop version of the page (Chrome for Android can do this, other browsers should be able to as well), you can still use roll20 on a mobile device. It'll be really bad because the screen space is tiny, but it'll work at all if you just need to do that for a bit.

I made some stupidly simplistic After Sundown helper apps. One draws karma cards, one lets you roll dice. Our group stopped playing after sundown so I stopped improving them once they just kinda worked at the basic level.

There's a more general Dice Roller that I experimented with which you might be able to use, though honestly I even forget how most of the interface works on that one.