Is it potentially possible foy Oyster pre-pay to be topped up when
using a bus Oyster reader? I can't use my Oyster on the tube cos I get
priv fares, but the top-idea sounds a good idea.

The automatic top-up seems OK as long as there are some checks and balances
involved, such as limits to how often the top-up can be applied and perhaps
an SMS sent out every time it is applied, just in case cards fall into the
wrong hands.

However if this is the case more has to be done to assist people in
collecting the top-up. I mostly use my Oyster on buses and trams and simply
don't use it on tube gates on a regular basis and I know many are in the
same boat. It would certainly help me if tube stations had Oyster readers
whose sole function was to allow passengers to check the status of their
Oyster cards and collect any top-up. I pass through tube stations quite
regularly but only use paper tickets on the gates.