EA DE released a .pdf document today about The Sims 4 Spa Day that contains an official description and features.
Luckily, @TheSimplyNando was generous enough to translate the entire text in English for us!
Be good to your Sims for a whole day with The Sims 4 Spa Day. Sims can visit now the brand new spa called ‘Perfect In Balance’ to get a revitalizing massage and find an inner balance by doing yoga. After a relaxing mud bath your Sims can forget the daily stress in the sauna. With a bunch of completely new objects and decoration pieces you can give your Sims’ homes a comfortable ambiance.
Brand new spa lot “Perfect In Balance”:
This brand-new lot has a calming and inviting atmosphere. Because of many activities and amenities even the most stressed out Sims recharge new energy. Choose between four pre-built spa lots or build your own one!
Do some wellness:
With the new wellness skill your Sims learn to control their spirit, body and feelings. Practise yoga or meditate to reveal the secret about teleportation and levitation.
Massage, Steam, Relaxation:
From the hotstone-massage to the reflexology-massage, your Sims can now get or give massages with some positive and negative effects. Relax in the sauna whilst mischievious Sims play smell-intensive pranks to other Sims.
Comfort from the top to the bottom:
Gentle hairstyles! Comfortable casual wear! You don’t have to sacrifice your style in the name of the comfort but it’s just a question of time until your Sims get used to their casual look!
Bring zen into your homes:
Build a mud bath and a sauna for the daily use! Equip your Sims’ homes with all the amenities and comfortable furnitures so they will never want to leave their house again.