Another solution is TapCrowd's lead capture iPad app for exhibitors. Our app can be used by your sales team to enter leads, and it can be offered in "kiosk" mode (self-service) to your booth visitors. Lead data is synced to your Marketo lead database. More info on Launchpoint:
https://launchpoint.marketo.com/tapcrowd/1870-lead-capturing-on-tradeshows/