How would it stand with the Highway Code, using these insread of an arm signal...
<goes away to check>
Hmmm.
Rules say you must 'indicate clearly'. Additional PDF on signals to other road users describes arm signals as "For use when direction signal indicators are not used, orwhen necessary to reinforce signal indicators and stop lights. Also for use by pedal cyclists and those in charge of horses". So it doesn't actually say it has to be an arm signal. Ok...
So I guess it depends on whether the indicators are 'clear'. Personally, I wouldn't trust them alone, because I think they'd be too close together to give a clealr message from a distance and drivers are not expecting a pedal cycle to have them, and instead will be looking for (assuming they care) an arm signal. Interesting then, that the definition of 'clear' might depend as much on the perceptions of other road users as on the inherent clarity of the device...
Which is a roundabout way of saying, I'll stick to arm signals. I suspect a stripe of scotchlite down the arm culminating in an arrow on the glove would be be more effective in the dark, and a bright yellow sleeve more effective in the light.