Hi Andy... good point/question...
While others are developing apps which bring some additional adjustments and more advanced simulations for fuel usage and tyre wear etc... I believe the official app from Scalextric does a really great job... and hence is a tough act to follow!
Meanwhile I, and a number of others, have done some more basic testing of the BLE protocol. It is very easy to set up simple comms between the ARC PRO and either an iOS or Android phone/tablet. All much easier than I had expected - so thanks Scalextric/Hornby for sharing the protocol.
I really like the standard ARC App which works very nicely on my iphone 5s, iphone SE and ipad mini. They call screen-mirror nicely onto my livingroom HD TV. Excellent!
Where I plan to make a contribution, with respect to the BLE protocol, is a very simple app which confirms all controllers and all sensors are functionng correctly... i.e. a very simple diagnostic app.