Flipkart's new service is a limited period offer and is available for an additional charge of Rs. 140 per item.

Flipkart has intensified competition in the online shopping segment with its new “same-day guarantee” scheme. Flipkart's same day delivery service is currently available for 10 cities - Bangalore, Delhi, Mumbai, Noida, Gurgaon, Faridabad, Kolkata, Manesar, Navi mumbai and Thane.
The same day guarantee service is available for an additional charge of Rs. 140 per item (introductory price). It's worth pointing out here Flipkart's new service is a limited period offer and is valid for items between April 28 to April 30 (orders placed before 12pm). According to Flipkart, the order would be delivered by 9 PM on the date promised during checkout.
Flipkart also notes: “If Flipkart is not able to deliver the item in the Guaranteed promise time, you get the product for free (upto Rs. 5000) as part of our money-back Guarantee. For Cash-on-Delivery orders, the shipment value will be collected as part of the order, but will be automatically refunded to your Wallet within 24 hours in case of delay from our side.”
Here's how you can avail Flipkart's same-day delivery service:

With competition heating up in the online shopping segment, e-commerce websites are under pressure to improve their services as well as come up with attractive offers – a trend that will certainly benefit the customers.
That said, same day delivery concept is already a huge hit in the West. However in India, there are several challenges such as creating a robust network, managing logistics, customer service and more.
It's worth pointing out that Amazon and Flipkart have already launched their next day delivery services.