GitHub Gist

The simplest option when you just want text you can edit by hand, from your phone, and have the snippet pick it up.

Steps

1. Go to gist.github.com, create a gist with one file, e.g. today.txt. Public or secret both work; secret is not private, just unlisted.
2. Click Raw. The URL looks like https://gist.githubusercontent.com/USER/ID/raw/COMMIT/today.txt.
3. Remove the commit hash so the link always returns the latest version: https://gist.githubusercontent.com/USER/ID/raw/today.txt
4. Paste that into a Dynamic snippet.

Edit the gist in the GitHub app or web whenever the text changes. Updates can take a minute or two to show up because of caching.