UnicodeMap lets you browse Unicode characters by range and search for them by name, display them (when Android has the font) and copy them to the clipboard. It can also decode a string of Unicode characters to names. Of course, Android will only properly display a minuscule fraction of the characters, but those that are not properly displayed still “work” in the sense that you can copy them around or whatever.
Although APK downloads are available below to give you the choice, you should be aware that by installing that way you will not receive update notifications and it's a less secure way to download. We recommend that you install the F-Droid client and use that.Download F-Droid