Dear Sir,
We have just finished a similar app which is for liquor stores. It has exactly the feature as you have defined. If you want to take a look at what we have done in the app and check it out yourself, please send me a device id of your iphone so that i may send you a build and a link to the admin panel so that you may test the app.
This way, you will definitely know my and my team's skills with geofencing using google's api.
I think there is no need to show you any other apps defining several other skills that we have as it would not be relevant. Still, if you need to see how many apps we have done which are on the app stores (iphone and google), let me know and i will be more than happy to show off a little.
I hope this is an interesting proposal that i am writing and that you will contact me when you are done reading it.
Looking forward to your response.
Umar
S3 Technology