This would depend on how you charge for these, virtually anything is possible.
Conferencing - maybe product timers
Gym - subscriptions handeled as product timers or payasgo as plain products.
Bookings, depends what you mean, room accounts or reservations - see below
Depending on you size Room Reservations would be my main area of concern.
There has been simple table reservation systems done in samba but personally I think it would be an ENORMOUS job to create a booking system.
If you do bookings external and just want room accounts then that is easy.
If you have many rooms and use a booking system - if the booking system which would offer features like online booking and chanal management I would personally look at creating the interface.
Not sure if you have seen it but I have been working on an interface to make samba work with NewBook PMS and the plan for this is for SambaPOS to handle all POS and Wet/Dry sales and feed these sales figures into the PMS for a central account/reporting source. This is for a 35 room hotel in Cotswolds.
Especially for this size I would only recommend this type of method as the features like online booking and chanal management are vital and adding these to the mix its not economical to setup everything in samba.
This said this is all depending on size and what you do for actual reservations.
The alternative is bookings handled on 3rd party but ALL accounts handled in samba which is more achievable.
Some key points in regards rooms is that not all the tariff should be accommodation sales if you are offering B&B or half board and the kitchen needs the sales from these aspects to accurately account their GP.
This would be doable in samba its just working out the best way.
The previous system went allong the route I would try first in samba which would be you set the tariff - probably as a product - and automate a process of refund/sale to ‘transfer’ the sales value to a different department/product group code.
Something allong the lines of;
£100 Tariff Product. (Accommodation GroupCode)
(not sure what event would work)
-£20 BreakfastAllocation Product (Accomodation GroupCode)
+£20 Breakfast Product (Food/Breakfast GroupCode)
Which would result in sales figures of;
Accommodation £80
Food/Breakfast £20
Preferably it would be better to have a action/‘back office’ way to do this like a transaction document type however these are for accounts rather than report figures.
I guess the alternative would be to add multiple sales accounts for your departments and base the target account on your product groupcode so that you can move values between sales accounts rather than have a single sales account and rely on reporting for sales breakdown (@Jesse am i getting there with my accounts understanding 
)
However this would require some help from someone with more samba accounts experience than me.
I personally cannot dedicate time to this route as have opted for the 3rd party integration given that the 3rd party is a full PMS system with many features which would take one person a lifetime to setup within samba (if all were possible)
This is my work to date on the NewBook integration, and although not complete there is nothing left which should cause too much of a snag that would make the link not posible (well hope not as hotel is expecting the system installed late Jan LOL)