Simple multiplattform mobile App

We require a mobile application for managing a customer database. The functional requirements are fairly simple: - Search for a customer: *City, Zip code, phone number, name, customer type... * "Around me" (customers of a certain type, located around current user's location) - Customer Details * View a specific customer's data: name, phone number, .... * EDIT customer's data - New customer found * Enter new customer's data (very similar to customer details page), get current location as customer's location. The customer information is stored in an SqlServer database on a server. It is quite big, containing about 500,000 customers. It also has already working browser apps for PC, developed in ASP.NET web forms. We'd rather stay close to this technology server-side: al least to use .NET and C# and avoid new languages (PHP, ruby...). also, better web forms than MVC, if possible, but this is obviously less important. The server-side code should at least be able to update or insert customer data directly in the database. This is NOT a massive app (it would be used by no more than 10-20 internal users) yet minimum concurrency is to be considered. Also, performance is important considering the ammount of customers of the database. Probably, getting an in-memory user-filtered list of the 10,000 customers "around me" should help a lot. Technologically, we don't have any experience with mobile apps. Yet, we believe this kind of app is perfectly suitable for an HTML5 app rather than native. I understand that using certain libraries we can achieve cross-plattform HTML5 mobile apps with a single source code (Iphone and Adroid are minimum requierements). We are particularly fond of jQuery so using jQueryMobile seems like a good idea. Initially we dont' requiere publishing the app in the different app stores, accessing from browser is acceptable. Yet if developed in jquery mobile or other mobile HTML5 frameworks, I believe that publishing should be fairly easy with tools such as PhoneGap? About the project budget, our lack of experience doesn't let us know if the budget is too high or too low, please take it just as an idea and feel free to post lower or higher bids if it is under or overestimated. Finally, I'd like to mention that this is just an embryo to try this technology. We believe this app will need to grow substantially in the future, so we are also looking for someone who can help us is mid or long-term.