The University is piloting a piece of software called Vevox to replace TurningPoint for immediate in-class polling. Having attended a demo session yesterday it looks to be effective and most of the functionality seems to match our needs (with the possible exception of group competitions but I'm not sure how well used that was across the institution anyway). There are a limited number of user accounts but the plan is to increase the number with demand. You need an account to create a poll (either via a web interface or embedded into PowerPoint (PC only)) but anyone can participate in a poll as long as they have the meeting room ID. It seems to work well on mobile devices and voting is straightforward. Further information is available here:

https://warwick.ac.uk/fac/soc/cte/students-partners/academictechnology/academictechnologies/vevox