Hardware & software:
- Fantastical at https://flexibits.com/fantastical for $40/year from Rene Ritchie.
- Calvary at https://cavalry.scenegroup.co for free (beta) from Alex Lindsay.
- Amphetamine (Mac OS) for free from Andy Ihnatko.
- Spelltower + at http://www.spelltower.com for $4.99 from Lori Gil.