Low cost GSM/GPRS modules for purchase in India
1) Simcom SIM900A : 
SIMCOM manufactured SIM900A is a very low cost GSM/GPRS module used widely in India for cost sensitive applications.
Features :
- Dual-Band 900/ 1800 MHz
- GPRS multi-slot class 10/8
- GPRS mobile station class B
- Compliant to GSM phase 2/2+
- Class 4 (2 W @900 MHz)
- Class 1 (1 W @ 1800MHz)
- Dimensions: 24*24*3 mm
- Weight: 3.4g
- Control via AT commands (GSM 07.07, 07.05 and SIMCOM enhanced AT Commands)
- Supply voltage range: 3.1-4.8V
- Low power consumption: 1.5mA(sleep mode)
- Operation temperature: -40° C to +85°C
SIM900A is available for purchase in India
@ Complete board with all interfaces Amazon India at Rs.1024/-
TTL version is also available at Amazon at Rs.1650/-
with RS232 version at Amazon at Rs.1199/-
@ Rhydolabz India at Rs.680/- each
@ Digibay India at Rs.899/- each
With TTL breakout board @ NSK Electronics at Rs.1,200/- each
With TTL breakout board @ Probots at Rs.1,200/- each
With RS232 interface @ NSK Electronics at Rs.1,500/- each
With RS232 interface @ Rhydolabz India at Rs.1,909/- each
With RS232 interface @ OnlineTPS at Rs.1,942/- each
2) Neoway M660 : 
This is a very easy to use low cost GSM/GPRS module which i came across while designing a GPRS data logger product for my client. It has very big pins and easily hand solderable. It has got a very programmer friendly set of AT commands in which i was able to connect to GPRS using only three commands remaining commands are the same as SIM900A AT command set.
Features :
- Quad-band：850/ 900/ 1800/ 1900 MHz
- Supports TCP/ UDP/ FTP/ DNS
- TCP procotol stack support client mode, server mode, mix mode
- Multi-channe link
- Product certifications: CMIIT, CE, FCC
- Dimensions 22.0 * 18.4 * 2.8 mm
- Sensitivity -107 dBm
- Instantaneous current Max 1.8 A
- Operation current < 250 mA
- Standby current < 2.0 mA
- Operating temperature : -40~+85℃
- Operation voltage : 3.5~4.3V, 3.9 V recommended
- Packaging 28-pin LCC package
M660 module is available for purchase at ecomsolutions.in for Rs. 500/-
3) Neoway M600A :
M660A is a newer version of the M660A module with a price tag much lower than M660 targeted to compete with Simcom counterpart SIM900A in Indian market. M660A is a GSM/GPRS industrial wireless module that supports EDGE-Rx. With the ability to support Voice, SMS, and Data Services, It is widely used in Industrial and Consumer Devices as a drop in replacement for SIM900A.
Features :
- Dual-band:900/1800M or 850/1900M
- High reliability:Special EMI/EMC design, still as steady as a mountain with bad electromagnetic environment
- Support various protocols:
- TCP/UDP/FTP/DNS/HTTP
- TCP procotol stack support client mode / server mode / mix mode
- Multi-channe link
- Certificate: CMIIT, CE
Product specification:
- Sensitivity : – 106dBm
- Instantaneous current : Max 1.8A
- Operation current :<300mA
- Standby current : 1.5mA
- Operation temperature : -30?~+70?
- Operation voltage :3.5V~4.3V(recommended value3.9V)
- Connector :68Pin soldering-pan connector LLC
Neoway M660A is available for purchase in India at ecomsolutions for Rs.400/- each
4) Simcom SIM900 : 
Although SIM900 does not fit in the article for low cost modules, I am including it anyhow if someone finds the links useful. SIM900A is the stripped down version of SIM900 and its the SIM900 that includes a whole lot of features as below,
Features :
- Quad-Band GSM/GPRS 850/ 900/ 1800/ 1900 MHz
- Normal operation temperature: -20 °C to +55 °C
- GPRS multi-slot class 10/8
- GPRS mobile station class B
- Compliant to GSM phase 2/2+
- – Class 4 (2 W @850/ 900 MHz)
- – Class 1 (1 W @ 1800/1900MHz)
- Dimensions: 24*24*3mm
- Weight: 3.4g
- Control via AT commands (GSM 07.07 ,07.05 and SIMCOM enhanced AT Commands)
- SIM application toolkit
- Supply voltage range : 3.2 … 4.8V
- Low power consumption: 1.0mA(sleep mode)
- Operation temperature: -40°C to +85 °C
Specifications for Fax
- Group 3, class
- Specifications for Data
- GPRS class 10: max. 85.6 kbps (downlink)
- PBCCH support
- Coding schemes CS 1, 2, 3, 4
- CSD up to 14.4 kbps
- USSD
- Non transparent mode
- PPP-stack
- Point to point MO and MT
- SMS cell broadcast
- 0710 MUX protocol
- embedded TCP/UDP protocol
- FTP/HTTP
- Special firmware
- FOTA
- MMS
- RTC backup
- Serial interfaces UART,SPI,I2C,GPIO,PWM,ADC
Certificates
- FCC
- CE
- ROHS
- PTCRB
- GCF
- IC
- ICASA
- REACH
SIM900 is available for purchase in India
@ Digibay India at Rs.1,499/- each
@ Robosoft systems at Rs.1,990/- each
@ Rhydolabz India at Rs.2,111/- each
@ Thinkware India at Rs.2,500/- each
Also see :
- Difference between SIM900 and SIM900A GSM modems
- SIM908 AT commands
- SIM300 GPRS commands
- Low cost RFID readers for purchase in India
- How to order components from Digikey to India without Shipping charges