Here is a great list compiled by AviZ over at RCGroups o 3rd party apps for the Phantom 3 / Inspire 1. In addition to this I have added the price in British Pounds for each platform it supports.
Airnest – by Airnest Ltd @ www.airnest.com – iOS £18.99
Altizure – by Everest Inovation Tech @ www.altizure.com – Android FREE/ iOS FREE
Autopilot – by Auto Flight Logic @ www.autoflightlogic.com – iOS £22.99
DronePan (DP) – by Dennis Baldwin @ www.dronepan.com – iOS FREE/ Android (soon)
DroneDeploy (DD) – by DroneDeploy @ www.dronedeploy.com – Android FREE App but site subscription, free option available/ iOS (soon)
CoPilot Basic – by FreeSkies @ www.freeskies.org – iOS – Extra in App purchases of full version £14.99.
FpvCamera – by fpvBooster @ www.fpvbooster.com – iOS £6.99 – Extra in App purchases.
Litchi – by VC Technology Ltd @ www.flylitchi.com – Android £14.99 / iOS £10.99
MapPilot (MP) – by MME (Maps Made Easy) @ www.mapsmadeeasy.com – iOS £7.99
Ultimate Flight v3 (UF) – by Android Apps by Ken @ www.djiultimateflight.com – Android £12.48