DeployHQ allows you to not only choose from commits that have been pushed to your repository, but any tags that you've added as well. This is supported in both Git and Mercurial repositories.
When clicking the (change) link next to either the start or end commit before starting a deployment, you'll find three tabs in the dialog:
As well as the default Recent Commits screen, you'll find Tag List and Manual Commit Ref tabs. The Tag List will show a list of all tags along with their corresponding commit ref.