I need to create android and iOS app for my magento store. And with some research Ive managed to find a paid app
http://www.magentocommerce.com/magento-connect/simicart-magento-mobile-shopping-app-builder.html
What i need is a separate app developed in my store name which should be available in play store and apple app store for customers to download. Is there any extension in magento to develop an app using php and magento CMS alone?
Your questions seems a bit broad, but i try to bring some light into that.
If you want to dig into cross platform development, consider the different types of apps:
Native Apps
Created with the platform-specific tools and programming languages (Java+Eclipse for Android, Objective-C/Swift + XCode for iOS). They bring the fastest (because native) experience to your app and can provide full hardware-access (if needed). These apps can be downloaded via app-stores which requires also an approval of the app there. The effort to create an app for Android and iOS is nearly doubled as you have to create apps for every platform you want to serve.
Hybrid Apps
This term refers to apps created with (mostly) web-technologies such as HTML, CSS and JavaScript which are "translated" into native platform code. Popular frameworks of this kind are PhoneGap an dAppcelerator Titanium Mobile. The good thing is, that you only need to develop such an app once for both Android and iOS. The drawbacks are limited access to hardware features and it might not be as fast as a native app. You can put these apps into the app-stores which require approval. Be reminded to check if the app stores allow apps developed with the hybrid framework of your choice (I can remember there were some issues some time ago where - I guess - PhoneGap apps were not allowed in the iOS app-store).
Web Apps
This is actually an "app" which is executed via mobile browser. You might also consider mobile and/or responsive websites for this behaviour. No possibility to download this app from an app-store which also means: No request for approval needed by an app-store. Hardware-Access is very limited.
From what I see on their website, Simicart seems to create a hybrid app which can then be downloaded and uses their own synchronizatoin to interact with the Magento webshop.
What i need is a separate app developed in my store name which should be available in play store and apple app store for customers to download. Is there any extension in magento to develop an app using php and magento CMS alone?
I guess you are refering to the fact, that "simicart.com" shows up as the app-creator in the app-store.
I don't know if there is any company/person out there that creates an extension to build a mobile app who does not show up as app-creator then. This would mean there is the possibility to download the app-files which you have to put on your own in the app-stores then.
What might help you
If you do not find any app-creator extension, think of creating one on your own by using the standard Magento webservice interfaces for SOAP or REST.
