Apologies for this looong post:
Ok so having checked, there are a few Apple apps out now, Car-Check (?) and Torque seem to be available, I seem to remember though that Apple had to use WiFi to connect rather than Bluetooth so you may have to find the WiFi version of the VGate iCar adaptor, there is one out there I'm sure. This info was based on other car makes like Audi, but if you get a WiFi adaptor and an Apple app like Torque which works, you could use that.
How good the apps are, is anyone's guess as I haven't used Apple ones before. Worth a hunt on the iStore or what ever they call it.
You can check out the Foxwell NT range of handhelds (
https://www.gendan.co.uk/category_150.html) - the NT530 comes with one car make for free (pick PSA as it contains Citroen too) but you can add other makes if your missus has a different car from you, paying about £50 per additional car brand. Limited to PSA up to 2013 models.
Or if you can find one on eBay or elsewhere, there was a software and dongle called PSA-COM but I have yet to try that, the original gets great reviews but is in the £400 range, so the eBay version, is in the £50 range but haven't tried that personally, it could be great, could be rubbish.
The big issue is Citroen (and Peugeot) use a proprietary CAN and VAN bus system, for which the BSI is the gatekeeper and general network bridge, so traversing the networks (there are 5) requires vendors to know the exact CAN frame IDs to do all of the requests you would need, so this limits general purpose OBD stuff to raw engine codes and even then, not the entire list. Where PSA used the generic PIDS as per the OBDII standard, then these work to an extent but a lot of OBDII PIDS are manufacturer specific and not published, so it's hard for companies to come up with diagnostic software which works properly.
If you want to get the full low-down and have access to a laptop, then you can buy a DiagBox kit for about £80-£100 ish off eBay and then get the software in VM format, to run on VMWare Player, which requires no installation or fiddling and that is very good, but needs experience to use effectively, again not really for the faint hearted. (DiagBox is the official software and the one which comes with the kit is a pig to install, but you need the Lexia-3 interface it comes with, then you buy the software again on it's own but in VM format so you can just run it on a program called VMWare Player, as above - that version of the program costs about a tenner as it does not include the interface)