Normal bike to exercise bike?

[ScariestFairyByFar]

Can you buy something that does this? If so where?

I know someone who bought one if these. Is this what you meant?

www.wiggle.co.uk/tacx-sirius-folding-cycle-trainer/

Ruby any recommendations? dsf wants to get my mum one for her birthday.

They are quite heavy & can be very fiddly to set up, Good ones are expensive. What is your budget & is your mum engineering-minded?

Ours is a Tacx & my 12o techie son was screaming in fury at it recently. They are fiddly to say the least.
DH & I think OP should get her mum a regular stationary bike, unless maybe she's a TTer, in which case she'll be very picky about what she wants, anyway.

12 Yo, even.